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  • Physics  (10,646)
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  • 201
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 105-112 
    ISSN: 0887-6266
    Keywords: polystyrene ; single-molecule single crystal ; radiation resistance ; lattice image ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure of single-molecule single crystals of isotactic polystyrene (i-PS) was investigated by electron diffraction (ED). The nanoscale single-molecule single crystals were found to be more resistant to electron irradiation when compared to the larger crystals of many molecules, as indicated by both observation of ED and high-resolution electron microscopy with increasing radiation dose. It is proposed that since the single-molecule single crystals are very small, the secondary electrons escape more frequently from the crystal so that the radiation damage is reduced. Lattice imaging was achieved at room temperature in the case of single-molecule single crystals because of their stability to electron irradiation. Published 1998 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America. J Polym Sci B: Polym Phys 36: 105-112, 1998
    Additional Material: 8 Ill.
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  • 202
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2371-2378 
    ISSN: 0887-6266
    Keywords: liquid crystalline ; polymers ; X-ray diffraction ; fibers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and a partial characterization of segmented liquid crystalline polymers with 3,3′-diallyl-4,4′-dihydroxybiphenyl unit in the rigid moiety is reported. The general formula of polymers is [-p-C6H4-COO-p-C6H3(R)-p-C6H3(R)-OOC-p-C6H4-O-(CH2)nO-]x, with n = 6, 8, 10, 12, and R = —CH2—CH=CH2. All polymers have nematic liquid-crystalline behavior. At room temperature, annealed fiber samples of polymers show a complex polymorphism. Three phases have been isolated with very large unit cells accommodating 6 or 12 chains. The projection of the molecular packing in a plane perpendicular to the c axis is characterized by the organization of chains in a two-dimensional hexagonal or quasi-hexagonal array. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2371-2378, 1998
    Additional Material: 6 Ill.
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  • 203
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1981-1986 
    ISSN: 0887-6266
    Keywords: polystyrene ; poly(2,6-dimethyl-1,4-phenylene oxide) ; blend ; molecular relaxation ; low temperature relaxations ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular relaxation behavior in terms of the α, β, and γ transitions of miscible PS/PPO blends has been studied by means of DMTA and preliminary work has been carried out using DSC. From DSC and DMTA (by tan δ), the observed α relaxation (Tα or Tg) of PS, PPO, and the blends, which are intermediate between the constituents, are in good agreement with earlier reports by others. In addition, the β transition (Tβ) of PS at 0.03 Hz and 1 Hz is observed at -30 and 20°C, respectively, while the γ relaxation (Tγ) is not observed at either frequency. The Tβ of PPO is 30°C at 0.03 Hz and is not observed at 1 Hz, while the Tγ is -85°C at 0.03 Hz and -70°C at 1 Hz. On the other hand, blend composition-independent β or γ relaxation observed in the blends may be a consequence of the absence of intra- or intermolecular interaction between the constituents at low temperature. Thus it is suggested that at low temperature, the β relaxation of PS be influenced solely by the local motion of the phenylene ring, and that the β or γ relaxation of PPO be predominated by the local cooperative motions of several monomer units or the rotational motion of the methyl group in PPO. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1981-1986, 1998
    Additional Material: 6 Ill.
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  • 204
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1995-2003 
    ISSN: 0887-6266
    Keywords: semiflexible polymers ; persistence length ; viscosity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A numerical approach, based on the configurational distribution function of a polymer chain in flow, has been used to calculate the zero-shear rheological properties. Starting from a bead-spring representation of the chain, the stiffness is introduced by repulsive springs between next-nearest neighbors. The connection to models based on the bending equation and their limitation is discussed. To obtain a correct model of a semiflexible chain, an inhomogeneous spring constant has to be used. Calculations have been carried out for the free draining case, and a simple relation between the intrinsic viscosity, the translational diffusion coefficient and the persistence length for arbitrary solvent conditions is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1995-2003, 1998
    Additional Material: 5 Ill.
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  • 205
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1987-1994 
    ISSN: 0887-6266
    Keywords: toughening ; impact strength ; blend ; nylon 6 ; core-shell impact modifier ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Super-tough nylon 6 was prepared by using maleic anhydride grafted polyethylene-octene rubber/semicrystalline polyolefin blend (TPEg) as an impact modifier. The morphology, dynamic mechanical behavior, mechanical properties, and toughening mechanism were studied. Results indicate that TPEg with a semicrystalline polyolefin core and a polyethylene-octane rubber shell, possesses not only a better processability of extruding and pelletizing with a lower cost, but also an improved toughening effect in comparison with the maleated pure polyethylene-octene rubber. The shear yielding is the main mechanism of the impact energy dissipation. In addition, the influence of melt viscosity of nylon 6 on toughening effectiveness was also investigated. High melt viscosity of matrix is advantageous to the improvement of notched Izod impact strength. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1987-1994, 1998
    Additional Material: 9 Ill.
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  • 206
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2015-2018 
    ISSN: 0887-6266
    Keywords: branched polymer ; gelation ; chain transfer to polymer ; molecular weight distribution ; continuous stirred-tank reactor ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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  • 207
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 181-190 
    ISSN: 0887-6266
    Keywords: dynamics ; rigid-rod ; semidilute ; birefringence ; rotational diffusivity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamics of rigid-rod-like molecules are studied using rheo-optical techniques. Measurements of flow birefringence as a function of shear rate are utilized to understand the scaling behavior of rotational diffusivity with respect to concentration and temperature. The concentration scaling exponent increases with increasing concentration and the scaling laws are valid in narrow concentration windows. The Doi-Edwards (DE) scaling law Dr ∼ c-2, holds at very high concentrations (cL3 〉 150). The concentration scaling exponent decreases dramatically with increasing temperature at concentrations, cL2d 〉 1. Scaling of rotational diffusivity, with respect to temperature and solvent viscosity in the semidilute regime, does not follow the predictions of DE theory (and related caging ideas). On the contrary, a model proposed by Fixman was found to explain both the temperature and concentration dependence of the rotational diffusivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 181-190, 1998
    Additional Material: 11 Ill.
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  • 208
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2019-2024 
    ISSN: 0887-6266
    Keywords: divinylbenzene ; porous copolymer ; excess adsorption isotherm ; active centers ; adsorption azeotropic point ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The adsorptive properties of four porous copolymers were investigated. They contained different functional groups in the internal structure. Adsorption measurements were made using the static method. Three two-component and one three-component solutions with different physicochemical properties were used. The adsorptive centers of the copolymers were evaluated based on the analysis of excess adsorption isotherms of the polar solution component. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2019-2024, 1998
    Additional Material: 4 Ill.
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  • 209
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2471-2482 
    ISSN: 0887-6266
    Keywords: poly(3-hydroxybutyrate-co-3-hydroxyvalerate) ; fibers ; wide-angle X-ray diffraction ; birefringence ; infrared dichroism ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structure of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes has been analyzed through wide-angle X-ray diffraction (WAXD), density, infrared dichroism, and birefringence measurements. There are three different types of crystalline structure in these fibers: two of these are the two types of orthorhombic with different orientation modes (the ordinary c-axis orientation (c//Z), and the preferential orientation of c-axis to the direction perpendicular to the fiber axis (c⊥Z)); and the third is pseudohexagonal. The weight fractions of the three types of crystals and amorphous phase were analyzed combining the WAXD integrated intensity and density data. The relation between crystalline orientation factors obtained separately from the WAXD measurement and the infrared dichroic ratio is also discussed. The birefringence of these fibers shows negative and positive values, depending on drawing and annealing temperatures. Considering the intrinsic birefringence and weight fraction of the c//Z, c⊥Z, and pseudohexagonal crystals, birefringence of the amorphous phase was evaluated. The amorphous birefringence shows positive values and decreases with an increase in the annealing temperature. From the analyzed fiber structure, it was speculated that the c⊥Z and pseudohexagonal crystals are preferentially formed in the drawing process irrespective of the drawing temperature.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2471-2482, 1998
    Additional Material: 15 Ill.
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  • 210
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2835-2848 
    ISSN: 0887-6266
    Keywords: dielectric spectroscopy ; interfacial polarization ; Debye length ; particle size ; polymer blends ; laminates ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this article we will focus on the dielectric properties of laminates and blends of a partially conducting (the liquid crystalline copolyesteramide Vectra B950) and an insulating (polypropylene or mica) phase. Dielectric spectroscopy was used as a tool to obtain information about the influence of the dimensions of the conducting phase in these laminates and blends. With decreasing thickness of the conducting layer in the laminates, the measured permittivities deviate more and more from the values predicted using conventional dielectric mixture models. From this discrepancy it is possible to calculate the thickness of the charge layer (=Debye length) in the conducting phase and the thickness of this phase itself, using a model derived by Trukhan. This model incorporates not only conduction, but also diffusion of the charges. Similar experiments were performed on a system of Vectra B950 particles in a polypropylene matrix. After the derivation of a new model, which combines the Trukhan model for space charges with the Böttcher equation for dielectric mixtures, we could make a distinction between samples containing large and small particles. For samples containing small particles, it is even possible to determine the variation in particle sizes. However, the use of a Debye length of 1.1 µm obtained from the laminates resulted in particle sizes that were two times higher than the actual values. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2835-2848, 1998
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  • 211
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2865-2868 
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 3 Ill.
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  • 212
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2849-2863 
    ISSN: 0887-6266
    Keywords: nylon oligoamides ; new crystal structure ; morphology ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three-amide oligomers of nylon 6 and nylon 6 6 have been investigated using electron microscopy (imaging and diffraction), X-ray diffraction, and computational modeling. A new crystal structure has been discovered for the three-amide oligomer of nylon 6. This material crystallizes from chloroform/dodecane solutions into an unfolded crystal form that has progressively sheared hydrogen bonding in two directions between polar (unidirectional) chains. This structure is quite different from the usual room temperature α-phase structure of chain-folded nylon 6 crystals, in which alternatingly sheared hydrogen bonding occurs between chains of opposite polarity in only one direction. The occurrence of this new structure illustrates the extent to which progressively sheared hydrogen bonding is preferred over alternatingly sheared hydrogen bonding. Indeed, the progressive hydrogen bonding scheme occurs in the three-amide nylon 6 material even though it requires a disruption to the lowest potential energy all-trans conformation of the chain backbone, and requires all the chains in each hydrogen-bonded layer to be aligned in the same direction. We believe the presence of chain folding, which necessarily incorporates adjacent chains of opposite polarity into the crystal structure, prevents the formation of this new crystal structure in the nylon 6 polymer. In contrast, the three-amide nylon 6 6 crystal structure is analogous to the polymeric nylon 6 6 α-phase structure, found in both fibers and chain-folded crystals, and consists of progressive hydrogen-bonded sheets which stack with a progressive shear. In both structures, the molecules (≈ 3 nm in length) form smectic C-like layers with well-orchestrated stacking of 2.2 nm to form a three-dimensional crystal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2849-2863, 1998
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  • 213
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2869-2876 
    ISSN: 0887-6266
    Keywords: cyclopentadiene ; resins ; carbon yields ; carbon-carbon composites ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of thermosetting resins were synthesized via phase transfer reaction of allyl chloride and propargyl bromide with cyclopentadiene in the presence of a strong base. Feed ratios of 1 : 1, 3 : 1, and 5 : 1 allyl chloride to propargyl bromide were used to give resins with varying amounts of propargyl and allyl functionality. In all cases the resins could be thermally cured, without added catalyst, at temperatures below 275°C to give black, glassy, brittle materials with densities of 1.15. TGA evaluation of the resins, with heating to 1000°C, resulted in carbon yields ranging from 48 to 66% with increasing propargyl functionality causing increased values. Physical mixtures of ACP and PCP resins were also made and evaluated. Cure of the mixed materials also occurred below 275°C, and carbon yields were comparable to the corresponding APCP resin. APCP/carbon fiber composites gave good mechanical properties with flexural modulus values of 115-130 GPa and flexural strength values of 1000 MPa. Carbonization of 1 : 1 APCP/carbon fiber composites provided materials with interlaminar strength values of approximately 1.14 MPa. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2869-2876, 1998
    Additional Material: 9 Ill.
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  • 214
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2877-2886 
    ISSN: 0887-6266
    Keywords: ionomers ; NIR ; chemometrics ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Near Infrared (NIR) spectroscopy coupled with chemometrics techniques were utilized to study the composition and properties of styrene-sodium methacrylate ionomers. Predictive models were obtained for mol % ionic content, as well as for the ionic cluster glass transition temperature, storage modulus, and tan δ peak parameters. The results illustrate the feasibility of using NIR and chemometrics algorithms as a property predictive tool, as well as the potential for the development of full calibration models. The chemometric parameters are discussed based on correlations with ionomer NIR spectral features and the role water molecules play as a probe for the associated structure of the ionomer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2877-2886, 1998
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  • 215
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2887-2894 
    ISSN: 0887-6266
    Keywords: light-activated polymers ; cure kinetics ; photocure ; photopolymerization ; nucleation ; growth ; Avrami equation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The purpose of this article is to develop a mathematical model that describes photocure and photopolymerization kinetics. This model is neither wholly phenomenological nor mechanistic, but contains elements of both. We draw an analogy between the classical Avrami approach for first-order phase transformations and the kinetic phenomena that occur during photocuring, and take into account cure inhibition due to a decrease in mobility of the constituents. The result is an explicit algebraic two-parameter expression for the extent of cure versus time. More importantly, the two parameters have physical significance, and to some extent can be predicted a priori. The model is compared to three sets of unrelated data, and excellent agreement is obtained, except for part of the data at the onset of the reactions. Physical insight obtained by comparing our theory with experiments supports the existence of preferred sites for initiating the reaction, and indicates that irradiation is the rate-limiting step in the overall cure process in the limit of small irradiation intensities. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2887-2894, 1998
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  • 216
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2895-2904 
    ISSN: 0887-6266
    Keywords: polyamide 11 ; dynamic rheo-optical spectra ; deformation mechanism ; thermal treatment ; hydrogen bonds ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical analysis, coupled with polarized step-scan FTIR transmission spectroscopy, has been used to monitor the submolecular motional behavior of uniaxially oriented polyamide 11. The dynamic in-phase spectra depend upon the morphology of the samples as well as on the polarization direction of the infrared radiation. The lineshape features of the dynamic in-phase spectra and their relationship to sample deformation are analyzed on the basis of changes of the internal coordinates, the reorientation movement of several functional groups, and the thickness change of the film during the stretching cycle. Dynamic infrared spectra are helpful for deconvolution of overlapping bands on the basis of their different responses to the external perturbation, which sometimes cannot be resolved well by derivative spectroscopy or curve-fitting analysis. The lineshape features have been used to follow microstructural changes after isothermal heat treatment. Near the N—H stretching frequency, two bands at 3270 cm-1 and 3200 cm-1 are resolved and analyzed in terms of Fermi resonance between the N—H stretching fundamental mode and the overtone and combination modes of the amide I and II vibrations. The dynamic response of the N—H stretching mode correlates with the modulation of hydrogen bond strength in uniaxially oriented PA-11. After thermal treatment at the highest temperature (190°C), the dynamic response in this region is mainly caused by the modulation of crystals. In amide I region, three bands at 1680 cm-1, 1648 cm-1, and 1638 cm-1 are separated and assigned to hydrogen bond-free, hydrogen-bonded amorphous, and hydrogen-bonded crystalline regions, respectively. The dynamic responses of the hydrogen-bonded regions are more sensitive to external perturbation. Two components are found in the amide II region, and the band at 3080 cm-1 is assigned to the overtone resonance of the component with perpendicular polarization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2895-2904, 1998
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  • 217
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2905-2910 
    ISSN: 0887-6266
    Keywords: polyalkylthiophenes ; heterojunction ; BF3-diethyl ether ; electropolymerization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new kind of all-organic heterojunction consisting of polythiophene and its derivatives was prepared by the electrochemical method in the presence of boron trifluoride diethyl ether as supporting electrolyte on indium-tin oxide glass electrode. It was observed that sequential-different oxidation potential among layers of polythiophenes is a prerequisite for the heterojunction to show rectification effect. The carrier-flow of the three semiconductors for PBrT/PT/PMT heterojunction was discussed in detail. Its rectification ratio, barrier height, and ideality factor were 392 (±2 V), 0.89 eV, and 8.1, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2905-2910, 1998
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  • 218
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2911-2921 
    ISSN: 0887-6266
    Keywords: epoxy ; amine ; microdielectrometry ; conductivity ; conversion ; glass transition temperature ; curing ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three reactive epoxy-amine systems based on diglycidyl ether of bisphenol A (DGEBA) with 4,4′-diaminodiphenylsulfone (DDS), 4,4′-methylenebis [3-chloro 2,6-diethylaniline] (MCDEA), and 4,4′-methylenebis [2,6-diethylaniline] (MDEA), were studied during isothermal curings at 140 and 160°C. The simultaneous kinetic and dielectric studies allow to express conductivity, σ, in terms of conversion, x, and of glass transition temperature, Tg. The conductivity, σ0, of the initial monomer mixture and, σ∞ of the fully cured network are measured. It is found that: The glass transition temperature, Tg, versus conversion, x, curves follows the equation of Di Benedetto modified by Pascault and WilliamsThere exists a linear relation between log σ/log σ0 and Tg.So, it is possible to predict both kinetic and dielectric behaviors of these epoxy-amine systems by the knowledge of Tg0, ΔCp0, and σ0, respectively, glass transition temperature, heat capacity, and conductivity of initial monomer mixture, Tg∞ and ΔCp∞, and σ∞, respectively, glass transition temperature and heat capacity and conductivity of fully cured network. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2911-2921, 1998
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  • 219
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2931-2939 
    ISSN: 0887-6266
    Keywords: associations ; random copolymers ; self-diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The self-diffusion of four styrene-methylmethacrylate random copolymers dissolved in acetone, a thermodynamically bad solvent for the styrene sequences in the copolymer, were investigated by pulsed-field gradient NMR. The echo attenuations Sinc(q,t) are dominated by diffusion of clusters. At higher concentrations, physical gelation sets in (formation of a transient network), which is manifested in an anomalous, restricted diffusion at short observation times. The measured fluctuations of the positions of the chain segments in the transient network have an amplitude of about 100 nm. The free long-range diffusion attained at long observation times shows a much stronger concentration dependence than in the nonassociating solvent benzene. The results are in accord with light-scattering investigations. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2931-2939, 1998
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  • 220
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2923-2930 
    ISSN: 0887-6266
    Keywords: polymer blends ; crystallization ; diffusion ; composition inhomogeneities ; internal spherulite structure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Composition profiles develop around growing PVDF spherulites in a blend with PMMA. These profiles assume stationary courses after a certain crystallization time provided that the overall degree of crystallinity is not too high. The composition-dependent growth rate and the diffusion-controlled remove of the surplus PMMA from the spherulite surface are then in a stationary equilibrium. The internal structure of the spherulites will then be homogeneous, too. Upon isothermal crystallization of a PVDF/PMMA = 60/40 (wt %) blend at 160°C for at least 4 h, the spherulites internal degree of crystallinity xc as related to the PVDF fraction obeys the inequality 55 wt % ≤ xc ≤ 84 wt %. The overall PMMA content within the spherulites as averaged over its whole inside has been determined by IR microscopy. It amounts to about 15 wt %. In contrast, the PMMA content of the amorphous phase within the spherulites (averaged again over its whole inside) ranges between 28 and 52 wt %. This composition jumps at the spherulite surface to 52 wt %. From the slope of the composition profiles outside the spherulites that have a width of more than 50 μm, the effective chain diffusion coefficient in blends as averaged over both components can be calculated to amount to (250 ± 100) μm2h-1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2923-2930, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2941-2947 
    ISSN: 0887-6266
    Keywords: Case II diffusion ; stability ; multidimensional Stefan-like Problem ; asymptotic analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A well-known model of one-dimensional Case II diffusion is reformulated in two dimensions. This 2-D model is used to study the stability of 1-D planar Case II diffusion to small spatial perturbations. An asymptotic solution based on the assumption of small perturbations and a small driving force is developed. This analysis reveals that while 1-D planar diffusion is indeed asymptotically stable to small spatial perturbations, it may exhibit a transient instability. That is, although any small perturbation is damped out over sufficiently long times, the amplitude of any perturbation initially grows with time. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2941-2947, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2949-2959 
    ISSN: 0887-6266
    Keywords: ultrasound ; crystallization kinetics ; film formation ; polychloroprene ; shear modulus ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report the application of an ultrasonic shear wave reflection technique for the investigation of film formation and crystallization kinetics of one amorphous and two semicrystalline polychloroprene samples with different gel content. Both isothermal and temperature-dependent measurements of the complex dynamic shear modulus (G* = G′ + iG″) have been performed at a frequency of 5.32 MHz. The process of film formation during the evaporation of water is expressed by a stepwise increase of the shear modulus. For the semicrystalline samples a further increase, which is due to crystallization, can be observed. Film formation and crystallization are delayed for the sample with high gel content and its minor final modulus is explained by a lower degree of crystallinity. The time-dependent increase of the shear modulus due to the growth of spherulites has been analyzed by the Avrami equation combined with the Kerner model for the modulus of a two-phase composite (spherulites in an amorphous matrix). The dynamic shear modulus for the spherulites has been estimated by a model introduced by Halpin and Kardos. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2949-2959, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2971-2979 
    ISSN: 0887-6266
    Keywords: poly(paraphenylenes) ; viscoelastic ; creep ; physical aging ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The linear viscoelastic behavior of a poly(paraphenylene) with a benzoyl substituent has been examined using tensile, dynamic mechanical, and creep experiments. This amorphous polymer was shown to have a tensile modulus of 1-1.5 Msi, nearly twice that of most common engineering thermoplastics. The relaxation behavior, which is similar to that of common thermoplastics, can be described by the WLF equation. Outstanding creep resistance was observed at low temperatures, with rubbery-like behavior being exhibited as the temperature approached Tg. Physical aging was shown to interact with long-term creep, rendering time-temperature superposition invalid for predicting the long-term properties. The effect of physical aging on the creep behavior was characterized by the shift rate μ. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 70: 2971-2979, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2771-2780 
    ISSN: 0887-6266
    Keywords: drying ; semicrystalline polymers ; poly(vinyl alcohol) ; solvent removal ; modeling ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The drying mechanism of semicrystalline poly(vinyl alcohol) (PVA) was investigated. PVA samples of various molecular weights were crystallized by annealing at temperatures slightly above the glass transition temperature of PVA, and swollen in water for different time periods. The water volume fraction in the sample was measured using a buoyancy technique. The samples were dried in air at constant temperatures, and the drying kinetics were investigated using thermogravimetric analysis. The change in degree of crystallinity of the swollen polymer during drying was measured by differential scanning calorimetry (DSC) as well as by Fourier transform infrared spectroscopy (FTIR). The degree of crystallinity of the samples increased during drying, which in turn was found to alter the drying rate. The drying kinetics were faster at higher temperatures, for lower molecular weights, and for lower degrees of crystallinity. A mathematical model was developed to predict drying rates of semicrystalline polymers by considering the crystallization kinetics during drying. The model predictions included the thickness of the polymer sample, the degree of crystallinity of the polymer, and the water weight loss as functions of drying time. Model predictions were found to agree reasonably well with the experimental results. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2771-2780, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3001-3005 
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1313-1320 
    ISSN: 0887-6266
    Keywords: swelling ; polyacrylamide gels ; swelling in polymer solutions ; polymer-polymer interaction parameter ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Swelling behavior of polyacrylamide (PAAm) and polyacrylamide-co-polyacrylic acid (PAAm-co-PAAc) gels was investigated in aqueous solutions of monodisperse PAAms with molecular weights (Mw) ranging from 1.5 × 103 to 5 × 106 g/mol. The volume of the gels decreases as the PAAm concentration in the external solution increases. This decrease becomes more pronounced as the molecular weight of PAAm increases. The classical Flory-Huggins (FH) theory correctly predicts the swelling behavior of nonionic PAAm gels in PAAm solutions. The polymer-polymer interaction parameter χ23 was found to decrease as the molecular weight of PAAm increases. The swelling behavior of PAAm-co-PAAc gels in PAAm solutions deviates from the predictions of the FH theory. This is probably due to the change of the ionization degree of AAc units depending on the polymer concentration in the external solution. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1313-1320, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1321-1334 
    ISSN: 0887-6266
    Keywords: gloss ; rough surface ; specular reflectance ; correlation length ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A general expression for gloss within the scalar Kirchhoff's theory is derived in terms of the detector collecting angle, and two statistical parameters that characterize the surface roughness. Analytical expressions for gloss are derived for an exponential and a Gaussian correlation function, and numerical results for these and other quasi-exponential correlation functions are presented. It is shown that the incoherent contribution to gloss is significant in common polymeric surfaces. The latter implies that surface height correlations cannot be neglected in the evaluation of gloss. It is also shown that for a correlation function with a single characteristic length, gloss scales with the correlation length Lc in the same way as with the detector collecting angle. This fact can be used to determine Lc with a glossmeter, and an experimental method to achieve this is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1321-1334, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1335-1348 
    ISSN: 0887-6266
    Keywords: PEEK ; growth rate ; crystallization ; kinetics ; regime ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An optical microscope equipped with a video photograph system was used to follow the growth of spherulites. Under nitrogen atmosphere, the growth rates at 290 and 300°C suggest that when the melt of PEEK has been equilibrated for 15 min at 400°C, the subsequent crystallization behavior was nearly independent of the prior thermal history. Linear growth rates of crystallization of PEEK have been measuredin the temperature range of 260-325°C for melt-pressed films and solvent cast films. Detailed kinetic analysis indicated that PEEK exhibited an unmistakable regime II → III transition at 296 ± 1°C. The II → III transition was clearly present irrespective of the rather drastic changes in U*. It is interesting that the branching and crosslinking retarded the growth rate of PEEK, but a transition from regime II to regime III still existed. For melt-pressed films after equilibration at 400°C for 15 min, values of σ and q suggest that U* should be taken nearer to 1500 cal/mol in the case of T∞ = Tg - 30 K and 2000 cal/mol in the case of T∞ = Tg - 51.6 K. The Kg(III)/Kg(II) ratio (1.32) was not as close to the predicted value of 2 as was Hoffman's ratio. For PEEK, the Thomas-Staveley constant (β) should be closer to 0.25 or 0.3 instead of 0.1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1335-1348, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1349-1359 
    ISSN: 0887-6266
    Keywords: reaction-induced phase separation ; polysulfone-epoxy blends ; epoxy-anhydride networks ; polysulfone-modified epoxies ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction-induced phase separation in a blend of a commercial polysulfone (PSu) with diepoxide-cyclic anhydride monomers, was studied. The diepoxide was based on diglycidylether of bisphenol A (DGEBA) and the hardener was methyl tetrahydrophthalic anhydride (MTHPA), used in stoichiometric proportion. Benzyldimethylamine (BDMA) was used as initiator. PSu had no influence on the polymerization kinetics, the gel conversion, and the overall heat of reaction per epoxy equivalent. A kinetic model including initiation, propagation, and termination steps was used to estimate the distribution of linear and branched species in the first stages of the chain-wise copolymerization. This distribution, together with the PSu distribution, were taken into account in a thermodynamic model of the blend. The interaction parameter was fitted from experimental determinations of conversions at the start of phase separation, obtained under different conditions. The thermodynamic model was used to explain the complex morphologies developed in materials containing different PSu concentrations as well as their dynamic mechanical response. The shift in glass transition temperatures was explained by the fractionation of different species during the phase separation process. Phase inversion produced a significant decrease of the elastic modulus in the glassy state and a thermoplastic-like behavior of the material in the rubbery region. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1349-1359, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1371-1382 
    ISSN: 0887-6266
    Keywords: epoxy resins ; thermosets ; glass transition ; yield behavior ; fracture toughness ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of crosslink functionality (fc), molecular weight between crosslinks (Mc), and chain stiffness display on the thermal and mechanical behavior of epoxy networks are determined. Both fc and Mc are controlled by blending different functionality amines with a difunctional epoxy resin. Chain stiffness is controlled by changing the chemical structure of the various amines. In agreement with rubber elasticity theory, the rubbery moduli are dependent on fc and Mc, but independent of chain stiffness. The glassy moduli and secondary relaxations of these networks are relatively independent of fc, Mc, and chain stiffness. However, the glass transition temperatures (Tg) of these networks are dependent on all three structural variables. This trend is consistent with free volume theory and entropic theories of Tg. fc, Mc, and chain stiffness control the yield strength of these networks in a manner similar to that of Tg and is the result that both properties involve flow or relaxation processes. Fracture toughness, as measured by the critical stress intensity factor (KIc), revealed that fc and Mc are both critical parameters. The fracture behavior is the result of the fracture toughness being controlled by the ability of the network to yield in front of the crack tip. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1371-1382, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1361-1370 
    ISSN: 0887-6266
    Keywords: transcrystallinity ; PTFE fiber/PP composites ; heterogeneous nucleation ; crystal growth rate ; orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of shear rates on the transcrystallization of polypropylene (PP) on the polytetrafluoroethylene (PTFE) fibers has been quantitatively investigated using a polarized optical microscope equipped with a hot stage and a tensile testing machine. The PTFE fibers were pulled at different rates, from 0.17 to 8.33 μm/s, to induce a range of shear rates, about 0.02 to 1.16 1/s, in the PP melt adjacent to the fiber. The induction time, nucleation rate, and saturated nucleation density at the fiber surface were determined at various crystallization temperatures. It was found that both the nucleation rate and the saturated nucleation density increase with increasing shear rates. However, the induction time is significantly reduced. Based on the theory of heterogeneous nucleation, the interfacial free energy difference functions Δσ;TCL of PP on PTFE fibers at different levels of shear rates were determined and compared with that obtained from crystallization under quiescent conditions. Results showed that the magnitude of ΔσTCL decreased to be about one-third of that for the quiescent crystallization, when a shear rate of 1.16 1/s was applied. The application of a shear stress to the supercooled PP melt by fiber pulling leads to enhance the development of transcrystallinity. Moreover, both the thickness and the crystal growth rate of transcrystalline layers were found to increase with the increasing rate of fiber pulling, especially at low crystallization temperatures where regime III prevails (see text). Surface morphology of PTFE fibers was revealed using a scanning electron microscope and an atomic force microscope. It is argued that the presence of fibrillar-type features at the fiber surface is the main factor responsible for the development of transcrystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1361-1370, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1383-1392 
    ISSN: 0887-6266
    Keywords: BPFCB ; PFCB ; crosslinking ; thermal and mechanical properties ; low dielectric constant ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: As the minimum features in semiconductor devices decrease, it is a new trend to incorporate copper and polymers with dielectric constant less than 3.0 to enhance the performance of the devices. Two fluorinated polymers, poly(biphenyl perfluorocyclobutyl ether) (BPFCB) and poly(1,1,1-triphenyl ethane perfluorocyclobutyl ether) (PFCB), are newly developed polymers with dielectric constants below 3.0. These two polymers have a similar backbone structure, but PFCB has the capability of crosslinking. To know the implications of these two polymers in the semiconductor industry, properties that are important for the integral reliability of Integral Circuits (IC), such as thermal and mechanical properties, should be understood. This comparative study shows that the crosslinking in perfluorocyclobutane aromatic ether polymer can reduce vertical thermal expansion and increase glass transition temperature (Tg) while water absorption, crystalline-like phase, and dielectric constant are slightly increased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1383-1392, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1393-1399 
    ISSN: 0887-6266
    Keywords: PNLC ; UV cure ; polyurethane acrylate ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymer network liquid crystals (PNLC) have been prepared from ultraviolet-curable polyurethane acrylate (PUA) and a nematic liquid crystal mixture (BL002). Effects of monoacrylate type on film morphology, temperature-dependent off-state transmittance, and electro-optic performance of the film have been studied. Among three types of monoacrylates incorporated (EHA(2-ethyl hexyl acrylate), MMA (methylmethacryalte), NVP (N-vinylpyrrolidone)), EHA-based PUAs gave the greatest polymer-LC phase separation, lowest threshold (V10), and operating (V90) voltages, and the effect was more pronounced in monoacrylate/triacrylate systems than in monoacrylate/diacrylate systems. Contact angle measurement offers a clue to the observed morphology and electro-optic behavior. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1393-1399, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1419-1422 
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1401-1417 
    ISSN: 0887-6266
    Keywords: polyelectrolytes ; Brownian dynamics ; shear flow ; extensional flow ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The conformational and rheological dynamics of dilute solutions of polyelectrolyte macromolecules undergoing shear and extensional flow are modeled using Nonequilibrium Brownian Dynamics (NEBD) and Configuration-Biased Monte Carlo (CBMC) simulations. The mathematical model utilizes a bead-spring chain with charged beads that interact through a screened Debye-Hückel potential, and that also interact through stretching and bending forces. The diffusion (or Fokker-Planck) equation for the probability density of the positions of the beads of the chain is converted to a Stochastic Differential Equation (SDE), from which the simulation algorithm for the NEBD is obtained. The CBMC is used in the initial chain generation and in determining steady-state properties in elongational flows. Various conformational and rheological quantities, such as the stress and birefringence, are monitored, under both steady-state and transient conditions, with the primary independent variable being the salt concentration (parametrized through the Debye length) and the strength of interaction q, related to the degree of ionization of the chain. It is found that this model is able to describe qualitatively many of the experimentally observed features in such systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1401-1417, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1423-1432 
    ISSN: 0887-6266
    Keywords: recycling ; polyolefine modification ; mechanical properties ; SAXS ; disorder ; compatibilizer ; blend ; block copolymers ; polyethylene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends from polyethylene (PE) and polystyrene-b-polybutadiene-b-polystyrene star block copolymers (SBS) (thermoplastic elastomers) are studied with polyolefine recycling in view. Each component, dispersed in a heterogeneous blend, exhibits a two-phase morphology. This structure is investigated by small angle X-ray scattering (SAXS) and compared to mechanical properties as a function of SBS grade and content. Increasing the SBS content one observes a vanishing PE-related long period reflection, while an SBS-related peak emerges. Best mechanical properties are obtained at concentrations, where the width of the observed long period reflection is broadest. For a quantitative analysis of the SAXS, the interface distribution function (IDF) analysis is employed. Data are fitted with a function modeling arrangement as well as disorder of domains inside the two different kinds of dispersed grains. The analysis yields that the observed broadening of the long spacing peak is caused only by an increased fluctuation of the thicknesses of amorphous layers in the PE stacks. This fluctuation again decreases for SBS concentrations beyond 15 wt %. The effect is strongest for blends containing the SBS grade with the lowest molecular weight and is discussed in terms of its compatibilization effect. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1423-1432, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1433-1442 
    ISSN: 0887-6266
    Keywords: photoconductivity ; charge carrier ; fluorescence ; curing effect ; molecular aggregation ; polyimides with alicyclic diamines ; intermolecular interaction ; mixed layer packing ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photoconduction mechanism of a polyimide with an alicyclic diamine, PI(PMDA/DCHM), prepared from pyromellitic dianhydride (PMDA) and 4,4′-diaminodicyclohexylmethane (DCHM) was investigated. Its UV absorption spectra, fluorescence spectra, photoconductivity, and annealing effects on the photocurrent generation were measured and compared to those of CPD, N,N′-dicyclohexylpyromellitic diimide, and PI(PMDA/DMDHM) prepared from PMDA and 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane (DMDHM). Photoconductivity of PI(PMDA/DCHM) depends upon the degree of molecular packing between polymer backbones. PI(PMDA/DMDHM) has no photoconductivity, probably due to a barrier to their intermolecular packing by the existence of two methyl substituents. Photoconductivity of PI(PMDA/DCHM) would be the result of the weak intermolecular interaction formed by mixed layer packing arrangement between pyromellitic moiety of one polymer backbone and N-cyclohexyl ring of another one in the ground state. Radiation absorption of this weak intermolecular interaction immediately forms a charge-transfer complex in the excited state and produces radical cation and anion charge carriers, which lead to the photoconductivity in the bulk polyimide film of PI(PMDA/DCHM). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1433-1442, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1443-1450 
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; STEM ; dark field imaging ; chemical derivatization ; morphology ; semicrystalline ; amorphous ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Important chemical and mechanical properties in semicrystalline polymers are determined by the noncrystalline or nonordered regions. Hence, characterizing these regions is important in developing a morphological model to better define and predict the chemical and mechanical behavior of polymeric materials. With this objective, preferential tagging was accomplished by covalent linking of a heavy element to poly(ethylene terephthalate) (PET). In scanning transmission electron microscopy (STEM), contrast was obtained using a low concentration of thallium (0.4%), the tagging element, thus providing a map of the more accessible regions within the semicrystalline structure. Differential scanning calorimetry (DSC) and wide-angle x-ray scattering (WAXS) were used to characterize the PET film. Elemental analysis using energy dispersive x-ray analysis (EDAX) was used to confirm the presence of the heavy element in the tagged regions. The STEM imaging results were then compared with the characterization results from the DSC and WAXS measurements to gain an understanding of the domains and their size ranges in the semicrystalline microstructure of PET. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1443-1450, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1451-1463 
    ISSN: 0887-6266
    Keywords: bulk modulus ; heat capacity ; high-pressure ; poly(vinyl acetate) ; thermal conductivity ; transient hot-wire method ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal conductivity λ and heat capacity per unit volume of poly(vinyl acetate) (260 kg mol-1 in weight average molecular weight) have been measured in the temperature range 150-450 K at pressures up to 1 GPa using the transient hot-wire method, which yielded λ = 0.19 W m-1 K-1 at atmospheric pressure and room temperature. The bulk modulus K has been measured in the temperature range 150-353 K up to 1 GPa. At atmospheric pressure and room temperature, K = 4.0 GPa and (∂K/∂p)T = 8.3. The volume data were used to calculate the volume dependence of λ, \documentclass{article}\pagestyle{empty}\begin{document}$g = - \left( {\frac{{\partial \lambda /\lambda }}{{\partial V/V}}} \right)_T .$\end{document} The values for g of the liquid and glassy states were 3.0 and 2.7, respectively, and g of the latter was almost independent of volume and temperature. Theoretical models can predict the value for g of the glassy state to within 25%. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1451-1463, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3137-3145 
    ISSN: 0887-6266
    Keywords: X-ray analysis ; copoly(ester-imide) ; thermotropic liquid crystalline polymers ; random copolymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure of a thermotropic liquid crystalline copoly(ester-imide) prepared from p-hydroxybenzoic acid (48 mol %), 4,4′-dihydroxybenzophenone (26 mol %), and N,N′-bis(trimellitimide)hexane (26 mol %) has been investigated by X-ray diffraction. X-ray fiber diagrams of as-spun and annealed fibers contain a series of aperiodic layer lines reminiscent of those seen for fibers of other copolymers that have extended chain conformations and completely random monomer sequences. The positions of these layer lines were reproduced approximately in simulation of the X-ray scattering by a fully extended chain of completely random sequence, and the match was improved to within experimental error when we considered a stereochemically acceptable sinuous chain. This agreement was lost when the sequence statistics deviated were completely random. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3137-3145, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3147-3154 
    ISSN: 0887-6266
    Keywords: glass microfiber ; scattering ; polymer ; nonwoven fabrics ; polymer analogue ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Disordered fiber mats made of glass microfibers (GMF) were studied using small-angle light scattering (SALS), ultrasmall-angle X-ray scattering (USAXS), SEM, and optical microscopy. The morphological scaling of these materials in the micron scale was very similar to that of polymers in the nanometer scale. In some fiber mats, such as GMF, the structure is randomized at the time of formation, leading to a statistical analogy with the thermal randomization that occurs in nanometer-scale, high polymers. Analogues for the coil radius-of-gyration, persistence unit, and scaling regimes exist in such fiber mats and may be a useful feature both for modeling thermally equilibrated polymeric systems, as well as furthering the understanding of the physical properties of fiber mats through analogy with the theoretical understanding of thermally equilibrated polymeric systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3147-3154, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1-9 
    ISSN: 0887-6266
    Keywords: small-angle neutron scattering ; SANS ; polystyrene ; polyvinylmethylether ; radius of gyration ; Zimm analysis ; random phase approximation ; phase diagram ; polymer blends ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle neutron scattering was used to measure the radius of gyration and thermodynamics of blends of poly(vinylmethylether) (PVME) at dilute concentration in deuterated polystyrene (PSD). The data were analyzed using the Zimm equation and the random phase approximation theory. For PVME with a weight-average molecular weight of 38,400 the value of the radius of gyration, Rg, was found to be 47 Å in the limit of the concentration of PVME extrapolated to zero. Analysis of the temperature dependence of the Flory interaction parameter, χ/v0, indicates that phase separation should occur at approximately 300°C for a sample with φPVME ≅ 9%. No significant temperature dependence of Rg was found over the experimental range studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1-9, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 11-19 
    ISSN: 0887-6266
    Keywords: fluorescence emission technique ; dynamic light scattering ; reduced viscosity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, rheological, and fluorescence properties of a cationic water-soluble copolymer, naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer), poly(DSQADMAPM)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the cationic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. The salt and pH responsiveness inherent to the cationic copolymer systems is a function of ionic group type. Experimental results indicate that IE/IM increases steadily with increases in polymer concentration and IE/IM values for a given polymer concentration are higher in salt. At low pH values, IE/IM is high and excimer emission increases as the quaternary amino groups (R4N+) are screened out. Dynamic light scattering (QELS) measurements indicate that diffusion coefficients of the cationic copolymer increase and the hydrodynamic diameters decrease with increasing salt concentration. Viscosity studies reveal that the polymer coil shrinks as salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of thallium (Tl+) with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty in reacting with bound naphthalenes located in the shrunk polymer coil. The cationic copolymer is depicted as an expanded polymer coil in deionized water because of intra- and interchain repulsions. Consequently, salt addition breaks down the repulsions and enhances intrapolymer micellization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 11-19, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 665-671 
    ISSN: 0887-6266
    Keywords: clustering ; water ; wood ; adsorption ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Clustering behavior of water molecules during adsorption of water in wood was studied using the Zimm-Lundberg theory. The average cluster size of water molecules was determined with the help of wood adsorption isotherms at five temperatures. The effects of both relative humidity and temperature on average cluster size were studied. Average cluster size progressively increased with an increase in humidity. At humidities corresponding to fiber saturation, larger clusters were formed. Cluster size increased sharply with an increase in temperature at humidities close to saturation. Formation of large clusters at high temperature and humidities close to saturation is attributed to increased fraction of weakly bonded water and capillary condensation in such conditions. A description of adsorption of water in wood was provided in terms of average cluster size. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 665-671, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1091-1094 
    ISSN: 0887-6266
    Keywords: electrorheological fluids (ERFs) ; poly(dimethyl siloxane) gels ; artificial muscle ; electromechanical actuators ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1081-1089 
    ISSN: 0887-6266
    Keywords: liquid crystals ; acrylate ; photopolymer network ; dynamic mechanical analysis ; infrared dichroism ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article is concerned with molecular orientation in liquid crystal (LC) monomers and the retention of orientation in crosslinked network polymers formed from them by photopolymerization. This is of importance because anisotropic mechanical and physical properties can be beneficial in certain structural applications. To this end, linear viscoelastic behavior of liquid crystal photo-monomers was investigated with dynamic mechanical analysis, and molecular order was studied by infrared dichroism measured with Fourier transform infrared spectroscopy. Although the order parameter of the monomer could vary from 0.45 to 0.70, depending on temperature, the order parameters of the polymer samples varied only from 0.50 to 0.62 and depended on polymerization temperature and extent of cure. The mechanical anisotropy was found to be a complicated phenomenon that depended not only on the molecular order, but also on other factors such as free volume and network structure. The difference in the elastic modulus parallel and perpendicular to the alignment direction was as high as a factor of two in the glassy state, and a factor of three above Tg. In addition, different amounts of mechanical anisotropy could be induced by varying the cure conditions. Finally, different postcuring schemes could cause variations in mechanical behavior by advancing cure or by inducing secondary reactions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1081-1089, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1095-1105 
    ISSN: 0887-6266
    Keywords: interface ; interfacial thickness ; surface tension ; dynamic mechanical ; effective volume ; rheology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Core-shell impact modifiers are used to enhance the impact strength of thermoplastics such as polycarbonate. The shell of the modifier is designed specifically to interact with the matrix polymer because interfacial adhesion between the modifier and matrix is important in improving the impact strength. Several methods have been proposed to study the interactions at the modifier/matrix interface. One measure of this interaction is the strength of lap joints. The degree of interactions at the interface can be characterized as the thickness of the interfacial region where the chains of the two polymers mix. Yet another aspect is related to the effect of interfacial interactions on the dynamic mechanical properties of the blend. Previous studies have shown that the viscoelastic properties of these blends deviate from the emulsion models that have been proposed for such blends. The deviation of the measured viscoelastic behavior of these blends compared to that predicted by the models has been attributed to the formation of network structure of particles in the blend. The formation of the network structure is a consequence of larger effective volumes of the particles due to interactions at the interface with the matrix. This study provides a means of using rheological properties and the emulsion models to estimate the extent of interaction at the modifier/matrix interface. In blends used in this study it can be shown that the interactions between the modifier and matrix extend far beyond the boundary between the two and the estimated effective volume fraction of modifier is much larger than the actual modifier content in the blend. The effective volume fraction is frequency dependent and decreases with increasing frequency. The data suggest that beyond certain frequencies the modifier no longer interacts with the matrix and the system has properties similar to the matrix with holes. The data are presented which indicate that, within the range studied, lower modifier shell molecular weight results in a higher level of interaction with polycarbonate. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1095-1105, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 383-394 
    ISSN: 0887-6266
    Keywords: ion-selective membranes ; gel crystallization ; poly(siloxanes) ; crown-ethers ; calixarenes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A one-step procedure for the preparation of ion-selective membranes is described. The method employs the thermally induced gel crystallization of ultrahigh molecular weight poly(ethylene) (UHMW-PE) from a dilute xylene solution. After evaporation of the xylene, a microporous UHMW-PE film remains, which can serve as the support for liquid and polymeric ion-selective membranes. The addition of a membrane solvent and suitable receptor molecules to the xylene solution allows a one-step incorporation of these membrane components into the UHMW-PE support. The influence of the preparation conditions of the UHMW-PE support on the rates of the p-tert-butylcalix[4]arene tetraethylester-mediated transport of NaClO4 was studied. Two concepts to improve the life-time of the membranes are introduced. In a first approach, the addition of photocrosslinkable nitril-substituted siloxane copolymers to the membrane phase has been evaluated. The enhanced viscosity of the membrane phase reduces leaching of carrier and solvent molecules from the membrane into the aqueous phases. In a second approach, the solvent is omitted and the membrane-phase merely consists of a benzo-15-crown-5 or calix[4]arene modified siloxane-copolymer, which is substituted to such a degree that ion transport no longer has to take place via diffusion of host-guest complexes but by jumping of the cations from one fixed carrier to a neighboring carrier. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 383-394, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1115-1128 
    ISSN: 0887-6266
    Keywords: interface structure ; fluorescence energy transfer ; polymer blends ; latex films ; poly(methyl methacrylate) ; poly(butyl methacrylate-co-butyl acrylate) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Immiscible polymer blend films were formed by air drying aqueous dispersions containing mixtures of a high-Tg latex, poly(methyl methacrylate), and a film-forming low-Tg latex, poly(butyl methacrylate-co-butyl acrylate). Fluorescence energy transfer experiments were used to characterize the interfaces in these films, in which one component was labeled with a donor dye and the other with an acceptor. The quantum efficiency of energy transfer (ΦET) between the donors and acceptors is influenced by the interfacial contact area between the two polymer phases. As the amount of soft component in the blend is increased, ΦET approaches an asymptotic value, consistent with complete coverage of the hard polymer surface with soft polymer. This limiting extent of energy transfer is very sensitive to the total surface area in the film, with correspondingly more energy transfer at constant volume fraction for small hard particles. Some of the details of the energy transfer are revealed through a fluorescence lifetime distribution analysis. The presence of ionic surfactant (sodium dodecyl sulfate) in the dispersion from which the latex blend film is prepared reduces the cross-boundary energy transfer by 30%, which implies that in these films the surfactant decreases the interfacial contact. After annealing the surfactant-free blends above 100°C, we observe an increase in energy transfer, consistent with a broader interface between the two polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1115-1128, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1129-1139 
    ISSN: 0887-6266
    Keywords: polymer diffusion ; ambient temperature ; fluorescence ; latex films ; poly(butyl methacrylate) ; poly((acetoacetoxy)ethyl methacrylate-co-ethylhexyl methacrylate) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymer diffusion across interfaces at room temperature (21°C) was analyzed by direct nonradiative energy transfer (DET) in labeled latex films. Two modellatex polymers were examined: poly(butyl methacrylate) [PBMA, Mw = 3.5 × 104, Tg (dry) = 21°C] and a copolymer of 2-ethylhexyl methacrylate with 10 wt % (acetoacetoxy)-ethyl methacrylate [P(EHMA-co-AAEM), Mw = 4.8 × 104, Tg (dry) = -7°C]. Little energy transfer due to polymer diffusion was detected for the P(EHMA-co-AAEM) latex samples in the dispersed state or dried to solids content below ca. 90%, but above 90% solids, diffusion occurs among particles. For PBMA, diffusion occurs only after the film is dried (〉97% solids) and aged. In the dry PBMA films, it requires 4-5 days at 21°C to reach a significant extent of mixing (fm = 0.3-0.4). This corresponds to an estimated penetration depth dapp of 30-40 nm and a mean apparent diffusion coefficient (Dapp) of 5 × 10-4 nm2/s. The corresponding Dapp value for the dry P(EHMA-co-AAEM) sample is 5 × 10-2 nm2/s, and it takes about 25-40 min for this polymer to reach fm of 0.3-0.4 with dapp of 20-30 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1129-1139, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1141-1151 
    ISSN: 0887-6266
    Keywords: polymer gel ; poly(N-isopropylacrylamide) ; PNIPA ; volume phase transition ; hydrogen bond ; hydrophobic interaction ; free volume ; positronium ; positron annihilation ; methanol-water mixed solvent ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The macroscopic volume shrinkage and swelling of poly(N-isopropylacryl-amide) (PNIPA) gel induced by the compositional change in the methanol-water mixed solvent is correlated to the change in the nanoscopic free volume size and numerical concentration formed in the PNIPA gels. The free volume size and numerical concentration are estimated from the longest component appearing in the positron annihilation lifetime curves. The apparent free volume fraction calculated by the free volume size and numerical concentration, and dispersion of the free volume deduced by the size distribution are utilized to analyze the origin and location of the free volumes. The free volume parameters obtained by analysis of the positron annihilation data show various nanoscopic phases occuring within the PNIPA gels during the volume change, implying the variation of the strength of the interactions among the solvent molecules and the polymer chains of the PNIPA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1141-1151, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 841-850 
    ISSN: 0887-6266
    Keywords: specific volume ; Tait equation ; compressibility ; scaling parameter ; hole theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The pressure-volume-temperature (PVT) properties of three commercial samples of poly(dimethylsiloxane) are studied experimentally and theoretically in the temperature range 25-150°C and for pressure to ∼ 3 kbar. The Tait equation is employed to represent the data at elevated pressure. Isothermal compressibilities are computed for the three samples. The melt data are analyzed in terms of the Simha-Somcynsky hole theory, and scaling parameters of pressure, volume, and temperature are obtained. Satisfactory agreement between theory and experiment is found over the entire range of experimental pressures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 841-850, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1235-1245 
    ISSN: 0887-6266
    Keywords: PMMA ; mechanical properties ; ionomer precursor polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rigid-rigid blends made of ionomer and ionomer precursor polymer, based on poly(methyl methacrylate) (PMMA), have been investigated. Two series of blends have been prepared for studying mechanical properties. In one series, dynamic mechanical properties were determined over a wide range of temperatures. As the weight fraction of the ionomer was increased, there was a modest increase of modulus at ambient temperature and a very large increase in the rubbery modulus at elevated temperatures above the glass transition temperature of PMMA. In a second series of tests, tensile stress-strain measurements, made at an ambient temperature, were carried out over a wide range of blend compositions. For all blends tested, the mechanical properties exhibited a synergistic enhancement, i.e., average values of modulus, strength and fracture energy were all higher than expected based on the rule of mixtures. Measurements of fracture toughness also exhibited synergy, with a maximum value, higher than the value of either blend component, being attained in blends containing about 30 wt % of the PMMA ionomer. These results are interpreted in terms of a higher resistance to fracture of the more chain-entangled ionomer phase and good interfacial adhesion between the two components of the blend. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1235-1245, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 495-517 
    ISSN: 0887-6266
    Keywords: crystallization ; DSC ; multiple melting ; nascent morphology ; polyethylene ; synchrotron ; UHMW PE ; WAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nascent morphology of UHMW PE exhibits high melting point, high crystallinity, and increased WAXS line breadth relative to samples formed by melt crystallization. Different empirical relationships between crystal size and melting point are observed for nascent and molded samples. This differentiation is removed following nitric acid treatment of the nascent flake. Solid-state annealing behavior is differentiated by several regimes. Regime I is characterized by increasing crystallite dimensions and crystallinity at low annealing temperatures. Regime II[a] and II[b] is identified by double melting in DSC scans of moldings and nascent flake, respectively. The double melting is due to partial melting with incomplete recrystallization. Regime II[a] of moldings is differentiated from Regime II[b] of flake by an increase in melting point of the higher melting endotherm. Within Regime II[b], the partial melting of the nascent structure is sensitive to the distribution of morphological stability. Regime III is initiated at annealing temperatures approaching the zero heating rate melting point, and shows melting kinetics by DSC or time-resolved WAXS using synchrotron x-ray radiation. The superheat, partially associated with Regime III behavior, is sensitive to morphological heterogeneity and annealing history. Morphological models are discussed which highlight the role of noncrystalline regions and melting kinetics on the melting behavior of nascent form crystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 495-517, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 519-536 
    ISSN: 0887-6266
    Keywords: poly[1-(trimethylsilyl)-1-propyne] ; Monte Carlo simulation ; diffusion coefficient ; molecular dynamics ; gas solubility ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The bonded constants in the DREIDING force field have been parameterized for poly[1-(trimethylsilyl)-1-propyne] (PTMSP) from AM1 calculations of the dimer. The resultant force field has been validated through the simulation of amorphous cell density and x-ray data (d-spacing) and used to obtain diffusion coefficients for five gases (He, O2, N2, CH4, and CO2) from 0.5 ns NVT molecular dynamics using the Einstein relationship. In addition, solubility coefficients of these gases have been obtained from the particle insertion method of Bezus et al. and from a fixed-pressure Monte Carlo method which was also used to calculate sorption isotherms. In general, there is good to excellent agreement between experimental and simulated values of the diffusion and solubility coefficients for He, O2, N2, and CH4. Sorption isotherms and dual-mode parameters calculated from the simulation results for O2, N2, and CH4 agree very favorably with experimental data (no experimental data was available for He). In the case of CO2, diffusion and solubility coefficients as well as sorption isotherms are underestimated. The less satisfactory results for CO2 have been tentatively attributed to inadequacy of the generic nonbonded Lennard-Jones potential terms of DREIDING used in this study. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 519-536, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2197-2210 
    ISSN: 0887-6266
    Keywords: polycarbonate ; PMMA ; polyglutarimide ; crystallization ; segregation ; AFM ; SAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microstructure of amorphous polymer blends has been extensively studied in the past, but now there is a growing interest for polymer blends where one or more of the components can crystallize. In this study we investigate such blends, namely miscible polycarbonate (PC)/acrylic blends. Using small angle X-ray scattering (SAXS) measurements, combined with atomic force microscopy (AFM), electron microscopy (SEM), and optical microscopy, we demonstrate that the amorphous acrylic component mostly segregates inside the spherulites between the lamellar bundles (interfibrillar segregation). Varying the PC molecular weight or the mobility of the amorphous component (by changing its molecular weight and Tg) does not change the mode of segregation. So far qualitative predictions of the mode of segregation in semicrystalline polymer blends have been proposed using the δ parameter (the ratio between the diffusion coefficient D of the amorphous component in the blend and the linear crystallization rate G), introduced by Keith and Padden. Our results suggest that other parameters have to be considered to fully understand the segregation process. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2197-2210, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 937-958 
    ISSN: 0887-6266
    Keywords: thermodynamics ; heteropolymers ; phase diagram ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On the basis of a variational principle a quantitative theory is developed enabling a thermodynamic description in terms of mean field approximation of heteropolymer mixtures of macromolecules with an arbitrary distribution for both degree of polymerization and composition. Rather simple general equations are derived to calculate compositions and volume fractions of spatially homogeneous macroscopic phases as well as to find the cloud-point curve, spinodal, and critical points. Potentialities of general theory are illustrated for copolymers synthesized by traditional methods. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 937-958, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 931-936 
    ISSN: 0887-6266
    Keywords: potentiometric titration ; mathematical simulation ; neighbor effect ; interpolymer complexes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theory of the “neighbor effect” was applied for the description of the potentiometric titration curves of polyelectrolytes. Satisfactory results for poly(acrylic acid) were obtained by considering the effect of the two (at the right and at the left) nearest neighbors on the state of the monomeric unit in the limits of triads. The developed method was used for the determination of the degree of linkage of acidic groups in solutions of the interpolymer complexes. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 931-936, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 969-976 
    ISSN: 0887-6266
    Keywords: positron annihilation ; conducting polymers ; free volume in polymers ; electrical conductivity in polymer electrolytes ; analysis of positron lifetime spectra ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Positron lifetime spectroscopy has been applied to study the temperature dependence of free-volume properties in a solvent-free polymer-salt complex polyethylene oxide (PEO) doped with ammonium iodide (NH4I, with NH4+ ≈ 0.076) in the temperature range of 298-353 K. The observed lifetime spectra were resolved into three components and the longest lifetime, τ3, was associated with the pick-off annihilation of ortho-positronium (o-Ps) trapped by the free volume. The lifetime component, τ3, and its intensity, I3, both showed a significant variation with temperature, which followed a different course in the heating and cooling cycle. Changes in the temperature coefficient of τ3 and I3 were observed at T ≈ 328 K, the melting point of the sample. This behaviour is correlated to the temperature variation of the electrical conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 969-976, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1857-1872 
    ISSN: 0887-6266
    Keywords: hybrid polymers ; rheology ; reptation ; silsesquioxane polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report on the viscoelastic behavior of linear thermoplastic nonpolar hybrid inorganic-organic polymers. These materials have been synthesized through copolymerization of an oligomeric inorganic macromer with 4-methylstyrene where the inorganic portion of the material is a well-defined polyhedral oligosilsesquioxane (POSS), R7(Si8O12)(CH2CH2C6H4C=CH2), with R = c-C6H11 or c-C5H9. A series of 4-methyl styrene copolymers with approximately 4, 8, and 16 mol % POSS macromer incorporation were investigated. Rheological measurements show that the polymer dynamics are profoundly affected as the percent of POSS increases. In particular, a high-temperature rubbery plateau develops (where a terminal zone is not observed), despite the fact that the parent poly 4-methylstyrene is unentangled. It is also observed that the thermal properties are influenced as the percent of POSS incorporation increases, with increases in the glass and decomposition temperatures. The results suggest that interchain interactions between the massive inorganic groups are responsible for the retardation of polymer chain motion, a mechanism similar to the “sticky reptation” model conceived for hydrogen-bonded elastomers and developed by Leibler et al. [Macromolecules, 24, 4701 (1991)]. Control over the interchain interactions would also give rise to the observed increases in glass transition and the establishment of a rubbery plateau. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1857-1872, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1881-1888 
    ISSN: 0887-6266
    Keywords: actinometric optical emission spectrometry ; plasma/surface interactions ; nitrogenated plasma polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An actinometric optical emission spectroscopy (AOES) study of the trends in the concentrations of the plasma species H, CH, CO, OH, and CN in film-producing glow discharges of mixtures of isopropanol and nitrogen was undertaken. Conventional AOES was used to obtain the trends in the plasma concentrations of these species as a function of the proportion of nitrogen in the feed, Rn. A dynamic variant of actinometry in which trends in the concentrations of plasma species are measured as a function of time following the cutting of one of the principal gas flows was also employed to investigate the relative importance of gas phase and plasma/polymer-surface interactions in the production of the species of interest. Each of the above-mentioned species is produced, to some degree, by plasma/polymer-surface reactions. As revealed by transmission infrared spectroscopy, the films deposited contain C—H, C=O, and O—H groups. For Rn 〉 0, the films become nitrogenated, with both N—H and C≡N groups being present. As revealed by transmission ultraviolet-visible spectroscopy, both the optical gap and the refractive index of the deposited films decrease as Rn is increased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1881-1888, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1873-1879 
    ISSN: 0887-6266
    Keywords: plasma-enhanced chemical vapor deposition ; actinometric optical emission spectroscopy ; tetramethylsilane ; nitrogen ; oxygen ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Films were produced by plasma enhanced chemical vapor deposition (PECVD) of tetramethylsilane (TMS)-helium-argon mixtures with either oxygen or nitrogen in a vacuum system fed with radiofrequency power. Actinometric optical emission spectroscopy was used to determine trends in the concentrations of plasma species of interest (H, CH, O, CO, and CN) as a function of the ratio of the inorganic reactive gas (oxygen or nitrogen) to the monomer (TMS) in the system feed. As the ratio of oxygen to TMS in the feed is increased, the degree of oxygenation of the deposited material, as revealed by transmission infrared spectroscopy, is also increased. Similarly, the degree of nitrogenation of the films increases with increasing nitrogen to monomer ratio in the feed. Strong correlations exist between the plasma concentrations of the above-mentioned plasma species and film structure and composition. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1873-1879, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1889-1899 
    ISSN: 0887-6266
    Keywords: polymer ; blend ; cocontinuity ; phase inversion ; interface ; morphology ; elasticity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work the level of continuity and cocontinuity for blends of HDPE/PS prepared on a twin-screw extruder have been studied by both morphology and dissolution studies. Addition of SEBS as an interfacial modifier results in a shift of the percolation threshold for dispersed PS to higher concentrations. The region of phase inversion, however, is maintained at 70% PS. The shift in the percolation threshold to higher values is related to reduced elongation of the PS dispersed phase after interfacial compatibilization. These results indicate that an interfacial modifier significantly influences percolation phenomena without shifting the region of phase inversion. Models based on viscosity ratio have failed to predict the region of phase inversion in this study. Elastic effects are shown to be able to describe the basic tendencies. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1889-1899, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1901-1910 
    ISSN: 0887-6266
    Keywords: oxidative polymerization ; furan ; 3-methylfuran ; 2,2′,5′,2″-terfuran ; electron paramagnetic resonance ; ab initio calculation ; polymerization mechanism ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The oxidative polymerization of furan, 3-methylfuran and 2,2′,5′,2″-terfuran, induced by iodine in organic solvents having different donicity, was investigated by time-resolved electron paramagnetic resonance (EPR) spectroscopy. The reaction was monitored starting from the onset of the process and radical species arising from the monomers in early stages of the polymerization reaction were detected. The comparison between experimental and theoretical hyperfine coupling constants, obtained by simulated EPR spectra and theoretical ab initio calculations, respectively, allowed one to structurally characterize the above radical species, thus enabling mechanistic conclusions about oxidative coupling. Moreover, the analysis of the time evolution of EPR spectrum during the oxidative polymerization process was used for evaluating the relative amount of localized and mobile radical species along the polymer backbone, thus getting preliminary information about conjugation extent and electroconducting properties of the final material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1901-1910, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1919-1925 
    ISSN: 0887-6266
    Keywords: positron annihilation ; polymer electrolyte ; network polymer ; poly(glycidyl ether) ; polyether ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lifetimes of positrons have been measured for network polymers based on polyethers. From the temperature dependence of the lifetime of ortho-positronium (o-Ps), τ3, for the network polymer of poly(ethylene oxide-co-propylene oxide) [P(EO/PO)], an onset temperature for limited local motions of molecules, Tγ, and the glass transition temperature, Tg, were determined to be 57 and 201 K, respectively. For the network polymer of poly[EO-co-2-(2-methoxyethoxy)ethyl glycidyl ether] [P(EO/MEEGE)], Tγ and Tg were determined to be 57 and 185 K, respectively. For both specimens, above 270 K, the observed linear temperature dependence of τ3 was attributed to the thermal expansion of open spaces in a liquid state. In the temperature range between Tγ and 270 K, for the P(EO/MEEGE) network, τ3 was longer and its intensity was smaller than those for the P(EO/PO) network. These results were attributed to the increase in the size of open spaces for the P(EO/MEEGE) network polymer and the blocking of these regions by motions of side chains and chain ends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1919-1925, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1927-1934 
    ISSN: 0887-6266
    Keywords: side chain liquid crystal polymers ; β-relaxation ; rotation of mesogenic units ; compensation law ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A strong dependence of the rotational dynamics of the mesogenic units (β-relaxation) on the order of the mesophase was found in sidechain liquid crystal polymers. The preexponential frequency factor, \documentclass{article}\pagestyle{empty}\begin{document}$ f_{\beta \infty }^* $\end{document} and the activation energy \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm E}_{\alpha \beta }^{\rm *} $\end{document} of the β-relaxation rate both increase significantly (i.e., obeying a compensation law) with increasing order of the mesophase which is accompanied by a decrease of the mean lateral mesogenic distance. In this work, we show how these experimental results can be interpreted in a quantitative manner by using the general results of the coupling model for cooperative motions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1927-1934, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1911-1918 
    ISSN: 0887-6266
    Keywords: polymer solutions ; supercritical fluids ; non-Newtonian viscosity ; free-volume ; polydimethylsiloxane ; carbon dioxide ; viscoelastic scaling theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent measurements of the viscosity of polydimethylsiloxane (PDMS) melts swollen with dissolved carbon dioxide at 50 and 80°C by Gerhardt et al. have shown that classical viscoelastic scaling factors can be employed to superpose the viscosity curves for CO2-swollen melts onto the viscosity curve for pure PDMS at the same temperature and pressure. Here a free volume expression for the viscosity of a diluted polymer melt is combined with equation-of-state theories for the volumetric properties of PDMS-CO2 mixtures to develop models for the CO2 concentration-dependent viscoelastic scaling factors. Both the Sanchez-Lacombe and Panayiotou-Vera equations-of-state are investigated for this purpose. The predicted viscoelastic scaling factors are found to be in very good agreement with the data of Gerhardt et al. The model predictions show that mixing of gaseous carbon dioxide into the swollen PDMS phase is highly non-ideal, and that significant free volume is added to the melt upon carbon dioxide dissolution. The free volume added to the melt by dissolved carbon dioxide is the principal mechanism for viscosity reduction, relative to pure PDMS, in this system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1911-1918, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1935-1946 
    ISSN: 0887-6266
    Keywords: polybenzoxazines ; Mannich base ; Schiff base ; H-bonding ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal degradation of a series of polybenzoxazines based on bisphenol A and various aliphatic amines has been studied. Using the hyphenated techniques of thermogravimetric analysis-Fourier transform infrared spectroscopy (TGA-FTIR), and gas chromatography-mass spectrometry (GC-MS), the mechanisms of thermal decomposition have been proposed. It is also proposed that the Mannich base in polybenzoxazines plays a significant role in the thermal degradation of polybenzoxazines. The contribution of hydrogen bonding to the degradation mechanism of the Mannich base has been examined. The proposed mechanisms have also been supported through the thermal degradation study of benzoxazine model dimers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1935-1946, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1971-1980 
    ISSN: 0887-6266
    Keywords: poly(methyl methacrylate) ; TSDC ; space charge relaxation ; polarization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of the polarization time in the formation of the PMMA space charge relaxation has been studied. The study has been carried out by thermally stimulated depolarization currents of electrets formed by windowing polarization. The results obtained have been fitted to the general kinetic order model, and they are consistent with the existence of a space-charge polarization mechanism with the kinetic order of 1.14. The intensity of the peak maxima results in being a good indicator of the trapped carrier number evolution. For high temperatures and high electrical fields the saturation of this mechanism is achieved faster, which is attributed to a carrier mobility increase with these parameters. Finally, a compensation law has been found for space-charge-relaxation in PMMA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1971-1980, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1959-1969 
    ISSN: 0887-6266
    Keywords: miscibility ; transesterification ; kinetics ; polyarylate ; liquid crystalline copolyesters ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of poly(oxybenzoate-p-ethylene terephthalate) (POB-PET) and polyarylate were confirmed to be a partially miscible system by differential scanning calorimetry. When 60/40 POB-PET/PAr blend was annealed at high temperature (above 270°C) for several minutes, the ester-ester interchange (transesterification) in the blend took place immediately, as evidenced by Fourier Transformed infrared analyses. The analysis of the blend annealed at 290°C by 1H-13C nuclear magnetic resonance disclosed that there were four new diads appearing in 15 min and an additional one produced in 60 min during the heat treatment. The miscibility between POB-PET and polyarylate increased with the mol concentration of these new diads judging from differential scanning calorimetry. The evolution of the concentration of the diad ethylene glycol-isophthalate during the annealing can be described by a second-order reaction. The activation energy of forming the diad ethylene glycol-isophthalate was 26.5 kcal/mol, and the preexponential factor for the transesterification reaction is 3.7 × 108 min-1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1959-1969, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1947-1958 
    ISSN: 0887-6266
    Keywords: interfacial tension ; breaking thread ; polyamide ; polyethylene ; interface ; modifier morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Compared to the dynamic mixing process used in melt blending operations, most techniques for measuring the interfacial tension can be considered as virtually static. For this reason, in order to measure the interfacial tension of an A-B immiscible system in the presence of an interfacial modifier, the problem of migrating the modifier to the interface is a central issue. In this study, the influence of the addition of an interfacial modifier, a polyethylene copolymer ionomer, on the interfacial tension between two high-density polyethylenes and a polyamide is investigated. The breaking thread method is used and the interfacial tension is measured as a function of ionomer content. In order to enhance the likelihood of placing the modifier in closer proximity to the interface, various sample preparations are compared. In all cases, the interfacial tension significantly drops with increasing ionomer content and tends to a limiting value. It is shown, however, that the preparation of the system for the breaking thread experiment via coextrusion using a conical die brings the modifier in closest proximity to the interface. With this approach an additional 1.45 times reduction of the interfacial tension at 10% compatibilizer concentration (based on the mass of HDPE) is observed compared to the classical technique of preparation. Confirmation of this effect is demonstrated using X-ray photoelectron spectroscopy where analysis of the thread surface of the system prepared by coextrusion indicates a more than fourfold enrichment of interfacial modifier. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1947-1958, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2379-2391 
    ISSN: 0887-6266
    Keywords: block copolymer ; thermoplastic elastomer ; physical gel ; polymer micelle ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379-2391, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1669-1677 
    ISSN: 0887-6266
    Keywords: photo-assisted poling ; polymer dynamics ; polymer structure ; nonlinear optical polyimides ; high glass transition temperature ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have used combinations of light, heat, and electrostatic fields to investigate the orientation of nonlinear azo-chromophores chemically incorporated into high glass transition temperature (Tg) polyimides. A number of nonlinear optical polyimides have been synthesized in which the interaction between the nonlinear optical chromophore and the polymer main chain was systematically altered to determine to what extent this steric interaction influences the orientation of the nonlinear chromophore. Chromophores in polymers may be oriented by a number of methods: (a) polarized light at room temperature (i.e., photo-induced orientation or PIO), (b) polarized light and electric fields (i.e., photo-assisted poling or PAP) at temperatures ranging from room temperature to the polymer Tg, and (c) electric fields at Tg (thermal poling). While thermal poling and PIO are usually possible, PAP depends strongly on the molecular structure of the polymer. Previously we have shown that PIO can be accomplished at room temperature in a system where the nonlinear chromophore is embedded into the polyimide main chain via the donor substituent, and this orientation can only be thermally erased at temperatures approaching Tg. In this article we show that, whereas photoisomerization can efficiently depole donor-embedded polyimides in a matter of few minutes at room temperature, PAP does not induce any polar order. This behavior is in marked contrast to a structurally related, side-chain, nonlinear polyimide, in which the azo chromophore is tethered via a flexible linkage to the polymer backbone. In this case some PAP occurs even at room temperature, while no PAP is observed for a donor-embedded system with a similar Tg. We suggest that the orientation during PAP below Tg in the side-chain polyimide is primarily due to the movement of the azo side chains, and there is a very little coupling of this motion to the main chain. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1669-1677, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1679-1694 
    ISSN: 0887-6266
    Keywords: crystallization kinetics ; thermotropic liquid crystalline polymers ; polyimide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied the nonisothermal and isothermal crystallization kinetics of an aromatic thermotropic liquid crystalline polyimide synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 1,3-bis[4-(4′-aminophenoxy) cumyl] benzene (BACB) by means of differential scanning calorimetry (DSC). Polarized light microscopy (PLM) and wide-angle X-ray diffraction (WAXD) results confirm that this polyimide exhibits a smectic texture. Nonisothermal crystallization showed two strong and one weak exothermic peaks during cooling. The phase transition from isotropic melt to liquid crystalline state is extremely fast which completes in several seconds. The mesophase transition has a small Avrami parameter, n, of approximate 1. The isothermal crystallization of 253-258°C has been examined. The average value n is about 2.6 and the temperature-dependent rate constant k changes about two orders of magnitude in the crystallization temperature range of 6°C. The slope of ln k versus 1/(TcΔT) is calculated to be -2.4 × 105, which suggests nucleation control, via primary and/or secondary nucleation for the crystallization process. During the annealing process, a new phase (slow transition) is induced, which grows gradually with annealing time. At lower annealing temperatures (220-230°C), the slow transition process seems not to be influenced by the crystals formed during cooling process and its Avrami parameter n is ca. 0.3-0.4. However, the slow transition was hindered by the crystals formed during cooling process when annealed at higher temperature (230-240°C). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1679-1694, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1703-1711 
    ISSN: 0887-6266
    Keywords: complex shear modulus ; ultrasonic measurements ; dynamic-mechanical measurements ; acrylic-type copolymers ; film formation ; glass-rubber relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An ultrasonic shear wave reflection method was applied to study film formation and temperature dependence of the complex shear modulus (G*=G′ + iG″) in different amorphous films made of aqueous dispersions of acrylic-type copolymers. The data are compared with dynamic-mechanical measurements in the low frequency range. It is shown that the temperature dependence of the storage (G′) and the loss modulus (G″) for both methods can be fitted by the same set of parameters using the Havriliak-Negami function incorporating the Vogel-Fulcher-Tamman-Hesse equation for the temperature dependence of relaxation times. The temperature dependence of the relaxation times obtained from the fits to the ultrasonic shear modulus is compared to the shift factors of the dynamic-mechanical measurements. The agreement between both methods is good. This suggests an almost thermorheological simplicity of the samples for the main glass-rubber relaxation and demonstrates the capacity of the ultrasonic rheometer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1703-1711, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1713-1719 
    ISSN: 0887-6266
    Keywords: polymer ; diffusion ; free-volume theory ; inverse gas chromatography ; gravimetric sorption ; ethylene-propylene-diene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Self-diffusion and partition coefficients were measured for two commercial ethylene-propylene-diene copolymers (EPDM) and five solvents at infinite dilution using inverse gas chromatography. Mutual diffusion coefficients for solvents in EPDM also were measured for finite concentration using gravimetric sorption for three of the solvents. From the inverse gas chromatography experimental values for self-diffusion coefficients were obtained. Free-volume parameters were obtained through regression of the self-diffusion coefficient as a function of temperature. Mutual diffusion coefficients as a function of concentration were predicted using free volume theory and compared with experimental data obtained using gravimetric sorption. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1713-1719, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2449-2459 
    ISSN: 0887-6266
    Keywords: small-angle neutron scattering ; rigid-rod polymer ; thorny-rod polymer ; self-reinforcing polymer ; chain conformation ; persistence length ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chain conformation of a rigid rod polymer, poly(benzoyl paraphenylene), is determined in the melt using small-angle neutron scattering. The coherent scattering cross-section from blends of partially deuterated and hydrogenous poly(benzoyl paraphenylene) agree well with ideal rod scattering for q 〉 0.02 Å-1, indicating that the polymer chains are highly extended. Comparison of the results to a single chain-scattering function for chains of arbitrary stiffness yield a persistence length of ca. 130 Å. Pure component scattering at the lowest scattering lengths indicate that the melt is not molecularly homogenous, but is comprised of domains, potentially reflecting localized groupings of chains with similar backbone orientation. Furthermore, this mesoscopic structure depends on the processing history of the polymer in the melt state. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2449-2459, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2025-2032 
    ISSN: 0887-6266
    Keywords: polymer ; gas ; solubility ; diffusivity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An in situ gravimetric technique, employing an electrobalance, is described for determining the solubility and diffusivity of gases in polymers over extended ranges of temperature and pressure. Solubilities of CO2 in polystyrene at 35°C were measured as a test case; the results are in excellent agreement with the literature values determined by the pressure decay method. Solubility and diffusivity results are also reported for PVC-CO2 at 35°C and for PS-1,1,1,2-tetrafluoroethane at 30, 90, and 120°C. A comparison with other studies shows the in situ method to be more efficient and precise than the ones based on weighing the gas-saturated polymer under ambient conditions. The kinetics of gas sorption were analyzed in terms of two data reduction techniques to derive diffusion coefficients. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2025-2032, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2047-2056 
    ISSN: 0887-6266
    Keywords: polypropylene ; spherulite ; cocrystallization ; lamellae ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: During spherulitic crystallization of polymers, there is a tendency for low molecular weight and other less crystallizable entities to be rejected from the body of the spherulites. This rejection process causes a segregation of these species to those areas where spherulites impinge. As a result of this segregation, lamellar and spherulite boundaries have a tendency to become weak, often resulting in premature mechanical failure. The objective of this work, anthropomorphically speaking, is to develop a melt miscible blend system in which a propylene copolymer “fools” a polypropylene homopolymer into rejecting the copolymer to the spherulite boundaries as an impurity. However, once the copolymer arrives at these boundaries, the copolymer subsequently connects adjacent spherulites through cocrystallization of the propylene copolymer segments. It was found that addition of either a random ethylene-propylene copolymer or an isotactic-atactic block copolymer was able to yield the desired effect. Cocrystallization was confirmed by calorimetry, and segregation of copolymer and subsequent reinforcement at the spherulite boundaries was directly observed microscopically. Using this approach, toughness was increased with little loss in stiffness. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2047-2056, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2033-2046 
    ISSN: 0887-6266
    Keywords: spacer conformation ; solid-state 13C NMR ; smectic ; poly(ester imide)s ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several poly(ester imide)s based on 4-N-(carboxyphenyl)trimellitimide, 4-N-(carboxyethenylphenyl)trimellitimide, 4-hydroxy-N-(4-hydroxyphenyl)phthalimide and long aliphatic spacers have been investigated by different solid-state NMR techniques. The conformations of the methylene units were studied by the γ-gauche effect of the 13C chemical shift. In the frozen smectic LC phase, an alternating sequence of trans-conformations and disordered segments is predominant. In contrast, the spacers in the smectic-crystalline phase are capable of forming ordered trans-trans conformations. The amount of tt-conformations is found to increase with the spacer length and depend on the packing of the mesogens and the type of linkage between mesogen and spacer. The thermal stability above 100°C and the segmental mobility of the tt-conformations, as measured by 13C/1H wide line separation NMR, suggest a ropelike arrangement of the spacers. The tt-sequences are located in the outer parts rather than in the center of the spacer layer. Dephasing delay experiments on analogous polymers, which are deuteriated selectively in the four central methylene groups of the spacers, prove that these segments do not contain tt-conformations. Consequently, the ordering is due to the molecular constrains exerted by the rigid mesogenic groups and not by lateral van der Waals interactions between adjacent spacer segments. In a random copolymer with two different spacer lengths, the shorter spacer is found to be more extended than in the corresponding homopolymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2033-2046, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2057-2067 
    ISSN: 0887-6266
    Keywords: PTFE ; fillers ; UV radiation ; degradation ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The first part of a series of two, this paper analyzes the degradation of pure and filled PTFE under high energy UV radiation. The polymer morphology is first investigated using differential scanning calorimetry, highlighting the respective nucleating efficiency of TiO2 and CaF2 during polymer crystallization. Then, the various polymers are exposed to excimer laser radiation and observed under an optical microscope. The results indicate that the degradation is closely connected with microstructural parameters. In pure PTFE, scattering by crystallites and reflection on piles of lamellae control the nature and extent of the degradation. In filled PTFE, nature and concentration of fillers are the most important features governing degradation. When absorbing particles are added to PTFE, the damage is restricted to the surface and photothermal processes can modify the degradation from heterogeneous to ablative, depending on the filler content. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2057-2067, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2069-2083 
    ISSN: 0887-6266
    Keywords: PTFE ; fillers ; UV radiation ; degradation ; multiple scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The second part of the series, this article analyzes the way UV light propagates through pure and filled PTFE. We investigated the diffusiveness of the semicrystalline matrix as well as the effect of scattering and absorbing fillers (CaF2 and TiO2) on the attenuation. The UV-visible absorption curves have been determined by spectrophotometry. A theoretical calculation based on a four-flux multiple scattering approach allowed us to satisfactorily reproduce the experimental results, highlighting the respective importance of the coherent and the diffuse fields. In light of this model, we discuss the influence of multiple scattering on the extent of degradation when PTFE is exposed to a high energy UV radiation. This approach provides of a comprehensive view of the damaging effect of UV light on PTFE, showing a good agreement with the experimental results of the previous article. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2069-2083, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2085-2093 
    ISSN: 0887-6266
    Keywords: starch ; shear-thickening ; semidilute solution ; viscoelastic properties ; oscillatory shear flow ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The shear-thickening behavior of semidilute waxy maize (WM) starch solutions (90/10 DMSO/water) exhibit much of the behavior of classical nonlinear viscoelasticity. Small-amplitude oscillatory shear experiments were used to investigate the network structure formed during the shear-thickening regime. The solution viscoelastic properties of WM starch prior to the shear-thickening region could be described by the GLV model. The macromolecules behave as random coils with a longest relaxation time of 0.58 ± 0.03 s. For WM starch the observed shear-thickening region creates a stable, highly entangled network which resembles the behavior found in solutions in the concentrated regime. The longest relaxation time for the entangled solution is estimated to be 1.4 s. Semidilute solutions of normal maize (NM) starch in 90/10 DMSO/water do not exhibit a shear-thickening regime. The oscillatory shear data obtained before and after a thixotropic loop experiment were identical. The semidilute solution conformational dynamics of NM starch indicate some degree of rigidity in one of the components that constitute NM starch which might be associated with the helical structure obtained by amylose in DMSO. © 1998 John Wiley & Sons, Inc. This article is a US Government work, and, as such, is in the public domain in the United States of America. J Polym Sci B: Polym Phys 36: 2085-2093, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2095-2102 
    ISSN: 0887-6266
    Keywords: molecular motion ; polyisobutylene ; isolated chain ; ESR ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(isobutylene) (PIB) chains with a radical at the chain end were graft-copolymerized on the poly(tetrafluoroethylene) (PTFE) surface in vacuo at 77 K. The PIB chains tethered on the PTFE surface in vacuo were regarded as isolated chains from neighboring tethered PIB chains. The molecular motion of the ends of the isolated PIB chains was observed by an electron spin resonance (ESR) spectrometer in the temperature range from 3 to 125 K, which was lower than Tg of PIB, 200 K,1 and two motion modes were found: One is a quantum tunneling of the methyl group located at the chain end at 3 K, and the other is an interconformation transition with freely rotating methyl group at the end at 77 K, where the transition rate was estimated to be 15 MHz at that temperature. The transition rate increased with an increase in temperature. The activation energy of the transition was estimated to be 370 J/mol. The high mobility and low activation energy was attributed to the isolation of PIB chains in vacuo. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2095-2102, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 289-301 
    ISSN: 0887-6266
    Keywords: polydimethylsiloxane ; permeability ; sorption ; mixed gas permeation ; clustering ; acetone/nitrogen separation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The permeability of polydimethylsiloxane [PDMS] to acetone, nitrogen, and acetone/nitrogen mixtures has been determined at 28°C. In pure gas experiments, the permeability of PDMS to nitrogen was 245 × 10-10 cm3(STP) · cm/cm2 · s · cmHg and was independent of pressure. The permeability of PDMS to acetone vapor increased exponentially with increasing acetone pressure. PDMS is much more permeable to acetone than to nitrogen; acetone/nitrogen selectivity increases from 85 to 185 as acetone partial pressure in the feed increases from 0 to 67% of saturation. In mixed gas permeation experiments, the nitrogen permeability coefficient is independent of acetone relative pressure and is equal to the pure gas permeability coefficient. The acetone permeability coefficient has the same value in both mixed gas and pure acetone permeation experiments. Average acetone diffusivity in PDMS, determined as the ratio of permeability to solubility, decreases with increasing acetone concentration due to mild clustering of acetone in the polymer (because acetone is a poor solvent for PDMS) and changes in the polymer-penetrant thermodynamic interactions which influence diffusion coefficients. A Zimm-Lundberg analysis of the acetone sorption isotherm is also consistent with acetone clustering in PDMS. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 289-301, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2129-2139 
    ISSN: 0887-6266
    Keywords: adhesion hysteresis ; poly(dimethylsiloxane) ; JKR technique ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The JKR technique was used to determine the source and nature of the adhesion hysteresis present in modified poly(dimethylsiloxane) (PDMS) networks. As controlled excess amounts of the tetrafunctional crosslinker were added to the networks, the adhesion hysteresis increased. It was found that by poisoning the catalyst with a thiol the hysteresis could be significantly lowered, and completely removed in some cases. We believe that the adhesion hysteresis in this system stems from a complexation between the excess crosslinker and the catalyst. We found that the work of adhesion in this case is a function of the unloading rate. The unloading rate dependence of this chemical adhesion hysteresis was attributed to the rate of bond dissociation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2129-2139, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1821-1830 
    ISSN: 0887-6266
    Keywords: reverse osmosis ; poly(aminostyrene) ; benzenediamines ; acyl chlorides ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin-film composite reverse osmosis membranes of polyamides were prepared by interfacial polymerization. Various benzenediamines and poly(aminostyrene) were interfacially reacted with various acyl chlorides to prepare a skin layer of composite membranes. Among the membranes prepared from the structural isomeric monomers of benzenediamines and acyl chlorides, i.e., the same chemical composition but different in the position of functional groups on the aromatic ring, the membrane with the best salt rejection was obtained when the reacting groups forming amide are located at the same position on the aromatic ring. Membranes prepared by interfacially reacting various diamines with trimesoyl chloride revealed that the salt rejection depends on the linear chain structure of polyamides and network formed by crosslinking. Membranes obtained by interfacial polymerization of poly(aminostyrene) with trimesoyl chloride showed higher water flux but lower salt rejection than those obtained by interfacial polymerization of various benzenediamines with trimesoyl chloride. Membranes obtained here showed the typical trade-off behavior between salt rejection and water flux. However, membranes prepared by interfacially reacting trimesoyl chloride with a mixture of poly(aminostyrene) and m-phenylenediamine or a mixture of poly(aminostyrene), m-phenylenediamine, and diaminobenzoic acid showed a performance advantage over usual membranes, i.e., a large positive deviation from the usual trade-off trend. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1821-1830, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1839-1845 
    ISSN: 0887-6266
    Keywords: positron annihilation ; polymers ; free volume ; plasticization of polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Positron lifetime measurements in pure polyvinyl chloride (PVC) and in the plasticized PVC have been performed. Tricresyl phosphate was used as a plasticizer. Samples of the PVC were prepared with eight different plasticizer concentrations (from 0 to 35% of the plasticizer in the PVC). All of the measurements were performed in air at room temperature. A conventional fast-slow coincidence lifetime spectrometer was used for the measurements. Mean free volumes radii and fractional free volumes were calculated from the lifetime data. It has been found that the mean free volume radius is in the investigated region of the plasticizer concentrations, a linear function of the concentration of the tricresyl phosphate in the PVC. It seems that a polynomial fit can be used to describe the fractional free volume vs. the plasticizer concentration in the PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1839-1845, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1831-1837 
    ISSN: 0887-6266
    Keywords: block copolymer ; wormlike micelle ; fluctuations ; slow mode ; dynamic light scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic light scattering (DLS) has been used to explore the properties of asymmetric styrene-isoprene (SI) block copolymers in concentrated solutions. Concentrations were always well below those necessary to access the order-disorder transition in neutral good solvents. The samples include SI (10-50), SI (36-9), and SIS (10-100-10), where the numerical suffixes denote the block molecular weights in kilodaltons; experimental emphasis was placed on SI (10-50). The DLS intensity correlation functions in the neutral good solvents, THF and toluene, were dominated by a slow mode that first appeared at a concentration c+ ≈ 4 c*, where c* is the coil overlap concentration. The decay rate of this mode scaled approximately as the third power of the scattering wavevector, and the excess scattered intensity decreased with increased scattering angle. These results were tentatively ascribed to the onset of substantial concentration fluctuations, that exhibited cylindrical, or wormlike structures. Measurements in solvents of known selectivity, dioxane and cyclohexane, and on a copolymer of the opposite composition, SI (36-9), indicated that the intermolecular association was driven by the effectively repulsive interactions between styrene and isoprene segments, rather than by solvent selectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1831-1837, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1847-1856 
    ISSN: 0887-6266
    Keywords: electrical transport ; dielectric properties ; barium titanate ; carbon black ; epoxy resin ; relaxation processes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conductivity and dielectric constant of a three-component 0-3 composite of epoxy resin-barium titanate-carbon black (0-3 composites are systems in which the filler is in the form of 0-dimensional (point-like, disperse) particles in a three-dimensional polymeric matrix1) have been investigated both at DC and the frequency range of 20-106 c/s. The effect of barium titanate concentration on percolation threshold, critical indices and the mechanism of conduction has been examined. An attempt was made to describe the electrical properties of composites with models originally developed for two-component systems' dielectric-conductor. With increasing barium titanate concentration the agreement of experimentally found frequency dependencies of conductivity and dielectric constant with models based on Debye's equation was found to degrade. An adequate description of electrical properties of composites' dielectric-ferroelectric-conductor should be based on the Havriliak-Negami equation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1847-1856, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2761-2769 
    ISSN: 0887-6266
    Keywords: protein folding ; Lyapunov exponents ; computer simulations ; nonlinear dynamics ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A lattice model with Monte Carlo dynamics is used to carry out computer simulations of protein dynamics on a four α-helix bundle. The interaction energies in the model can be set so that either the helix bundle structure remains relatively stable or changed so that it unfolds. The computer model produces output that simulates experimental measurements relating to the structure. We show how this output can be used with analytical techniques of nonlinear dynamics to obtain important information about the complex underlying protein dynamics. Time-delay reconstruction plots of structural parameters of unfolding bundles resemble strange attractors in a space of dimension 3-4. We calculate Lyapunov exponents for these unfolding runs and find positive Lyapunov exponents implying chaotic dynamics. For stable runs the Lyapunov exponents are close to zero. We use these Lyapunov exponents to calculate the rate of loss of structural information during the unfolding process and show how the approach may be useful for investigating the folding dynamics of proteins. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2761-2769, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2717-2724 
    ISSN: 0887-6266
    Keywords: tussah silk ; fibroin ; methanol treatment ; α-helix structure ; β-sheet structure ; dynamic mechanical analysis ; thermomechanical analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal response of tussah (Antheraea pernyi) silk fibroin films treated with different water-methanol solutions at 20°C was studied by means of dynamic mechanical (DMA) and thermomechanical (TMA) analyses as a function of methanol concentration and treatment time. The DMA curves of α-helix films (treated with ≥80% v/v methanol for 2 min and 100% methanol for 30 min) showed the sharp fall of storage modulus at about 190°C, and the loss peak in the range 207-213°C. The TMA curves were characterized by a thermal shrinkage at 209-211°C, immediately followed by an abrupt extension leading to film failure. Both storage and loss modulus curves significantly shifted upwards for β-sheet films, obtained by treatment with ≤60% methanol for 30 min. The loss peak exhibited a maximum at 236°C. Accordingly, the TMA shrinkage at above 200°C disappeared. The films broke beyond 330°C, failure being preceded by a broad contraction step. Intermediate DMA and TMA patterns were observed for the other solvent-treated films. The loss peak shifted to higher temperature (219-220°C), and a minor loss modulus component appeared at about 230°C. This coincided with the onset of a plateau region in the storage modulus curve. The TMA extension-contraction events in the range 200-300°C weakened, and the samples displayed a final broad contraction (peak temperature 326-338°C) before breaking. The DMA and TMA response of these films was attributed to partial annealing by solvent treatment, which resulted in the formation of nuclei of β-sheet crystallization within the film matrix. The increased thermal stability was probably due to the small β-sheet crystals formed, which acted as high-strength junctions between adjacent random coil and α-helix domains. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2717-2724, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2961-2970 
    ISSN: 0887-6266
    Keywords: micelle ; blends ; crystallization ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization, morphology, and crystalline structure of dilute solid solutions of tetrahydrofuran-methyl methacrylate diblock copolymer (PTHF-b-PMMA) in poly(ethylene oxide) (PEO) and PTHF have been studied with differential scanning calorimetry (DSC), X-ray, and optical microscopy. This study provides a new insight into the crystallization behavior of block copolymers. For the dilute PTHF-b-PMMA/PEO system containing only 2 to 7 wt % of PTHF content, crystallization of the PTHF micellar core was detected both on cooling and on heating. Compared the crystallization of the PTHF in the dilute solutions with that in the pure copolymer, it was found that the crystallizability of the PTHF micellar core in the solution is much greater than that of the dispersed PTHF microdomain in the pure copolymer. The stronger crystallizability in the solution was presumably due to a softened PMMA corona formed in the solution of the copolymer with PEO. However, the “soft” micelles formed in the solution (meaning that the glass transition temperatures (Tg) of the micelle is lower than the Tm of the matrix phase) showed almost no effects on the spherulitic morphology of the PEO component, compared with that of the pure PEO sample. In contrast, significant effects of the micelles with a “hard” PMMA core (meaning that the Tg of the core is higher than the Tm of the PTHF homopolymer) on the nucleation, crystalline structure, and spherulitic morphology were observed for the dilute PTHF-b-PMMA/PTHF system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2961-2970, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2805-2810 
    ISSN: 0887-6266
    Keywords: poly(dimethylsiloxane) ; DSC ; raman spectra ; thermal history ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(dimethylsiloxane) was studied by laser Raman spectroscopy and differential scanning calorimetry. The Si—O—Si skeletal mode at 489 cm-1 and the C—Si—C deformation bands at 188 cm-1 and 158 cm-1 were studied as functions of temperature from ambient to -130°C, and effects of temperature interpreted in accordance with results from thermal analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2805-2810, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2793-2803 
    ISSN: 0887-6266
    Keywords: activation volume ; relaxation ; pressure ; nonlinear optical polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume of the side-chain copolymer poly(disperse red 1 methacrylate-co-methyl methacrylate) (DR1-MMA). The decay of the SHG signal from poled films of DR1-MMA was recorded at hydrostatic pressures up to 3060 atm and at different temperatures between 25°C below the glass transition temperature (Tg) to 35°C above it. The activation volume, ΔV*, decreased with increasing temperature. The data suggests that the coupling between chromophore reorientation and the long-range motion of the polymer is stronger for the DR1-MMA side-chain system than in previously measured guest-host systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2793-2803, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2781-2792 
    ISSN: 0887-6266
    Keywords: waterborne epoxy ; surfactant ; cooperativity ; Fox equation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated epoxies based on the diglycidyl ether of bisphenol A (DGEBA) cured with 2-ethyl-4-methylimidazole (EMI-24) in the presence of the nonionic surfactant Triton X-100. A goal was to determine if the viscoelastic properties of the epoxy-surfactant system differed when prepared in bulk form, as opposed to being cast as a thin film on the surface of E-glass cloth. Such a combination of materials has generated great interest for potential use in the construction of laminated circuit boards. Using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and atomic force microscopy (AFM), it was determined that the surfactant acts as a plasticizer and is miscible with the epoxy system in concentrations up to 15% by weight. The glass transition temperature (Tg) depression of the epoxy due to the surfactant was accurately described by the Fox equation. DMA master curves were constructed in the frequency domain. The temperature dependence of the shift factors was used to determine the fragility of each of the samples studied. It was found that the fragility (cooperativity) of the epoxy decreased as the concentration of surfactant increased, presumably due to a reduction of intermolecular constraints. The fragility of the combined epoxy-surfactant system increased when cast on the surface of the E-glass cloth. Results for our model epoxy-surfactant resin were in excellent agreement with those obtained using a commercially available aqueous waterborne epoxy resin. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2781-2792, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2811-2819 
    ISSN: 0887-6266
    Keywords: PTFE/hexafluoropropylene copolymers ; crystal ; disorder ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of new copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) containing up to 50 mol % of the hexafluoropropylene comonomer have been investigated with respect to chain conformation and crystal structure using wide-angle X-ray diffraction (WAXD). Increasing HFP content leads to significant departures from the highly ordered crystalline structure of the homopolymer PTFE; the helical conformation of the chain relaxes and untwists to accommodate the larger —CF3 pendant group in the HFP unit. Simultaneously the lateral hexagonal packing of the helices becomes less ordered and the a-dimension of the hexagonal cell increases. The above effects are progressive with increasing HFP content. At 50 mol % HFP incorporation the structure is a disordered crystalline phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2811-2819, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2821-2827 
    ISSN: 0887-6266
    Keywords: polypropylene ; composites ; gamma phase ; epitaxy ; X-ray scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method for crystallizing oriented samples of the γ-phase of isotactic polypropylene (iPP) under atmospheric pressure in the presence of nucleating fibers has been developed. The technique uses iPP grades of high molecular weight and high isotacticity and produces a mixture of α and γ-phase crystals within the matrix of both pitch-based carbon and Kevlar®-reinforced composites. Two-dimensional wide-angle X-ray scattering (WAXS) patterns from these samples show that the content of the γ-phase decreases as the fiber loading in the composites decreases, suggesting that the γ-phase is directly nucleated by the fibers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2821-2827, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2829-2833 
    ISSN: 0887-6266
    Keywords: Raman ; LAM ; stress ; polyethylene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman longitude acoustical mode (LAM) study of axially stressed polyethylene-made microfilms gave evidence of the formation of the straight tie molecules localized in two neighboring crystals and in an amorphous layer situated between them. The samples were bicomponent blends composed of polyethylenes with different MW (7 × 104 and 2 × 106). Each MW fraction exhibits an individual LAM band responding to crystals with the size specific to a given fraction. Under tensile stress, the bands shift insignificantly towards an exciting laser line. In addition, the LAM localized on all-trans sequencies with the length exceeding the mean crystallite size appear in the spectrum of a stressed sample. The reversibility of these spectral changes depends on the draw ratio of samples. We conclude the effect is due to stress-induced gauch-to-trans transformations taking place in the amorphous layers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2829-2833, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 300
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 107-118 
    ISSN: 0887-6266
    Keywords: polyoxymethylene ; elastomer blend ; drawn fibers ; mechanical properties ; structure relationships ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Superdrawn fibers of an elastomer-poly(oxymethylene) (POM) blend have been prepared and investigated in terms of the structure and mechanical properties. The development of the mechanical properties along the fiber axis and the formation of a higher order structure during drawing were slightly retarded by blending, but the loop tenacity increased greatly with the elastomer content. The blend microtextures had an immiscible and phase-separated morphology in which the elastomer was dispersed in the form of streaks between the oriented POM layers, which allowed the fiber to split into smaller filaments on bending. The high loop tenacity of the blend fibers is due to an increase in the radius of curvature resulting from the filament splitting on bending, because the shear stress at the bending corner becomes higher as the radius of curvature increases. © 1997 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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