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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of activities of homogeneous Ti-based catalysts in the presence of methylaluminoxane (MAO) for synthesis of syndiotactic polystyrene by UV/visible spectroscopic study (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1733-1741 
    Details
    ISSN: 0887-624X
    Keywords: homogeneous Ti-based catalyst ; methylaluminoxane ; catalytic activity ; UV/visible spectroscopy ; syndiotactic polystyrene ; polymorphic structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic activities in syndiospecific polymerization of styrene in hydrocarbon using homogeneous Ti-based catalysts in the presence of methylaluminoxane (MAO) were investigated through UV/visible spectroscopic analysis. A strong UV absorption band of CpTiCl3, itself, incipiently appeared at λmax = 400 nm in toluene, followed by a bathochromic shift with its remarkable decrease by the addition of MAO. The absorption band intensity at λmax = 400 nm arising from delocalization of π-electrons on the cyclopentadienyl ring decreased by methylation in the presence of MAO with regard to the mechanism for production of an active center (“cation-like”), for example, the change of the ionic nature. The intensity decrease at λmax = 400 nm was suppressed over 2000 of the [Al]/[Ti] ratio. In the case of Ti(OC4H9)4 having a σ-ligand, new and broad UV absorption bands were developed at λmax = 340 nm and 410 nm in the presence of MAO in contrast with the CpTiCl3/MAO system. Comparison between the relative absorption intensities at λmax = 340 nm and 410 nm led to the determination of a maximum catalytic activity of Ti(OC4H9)4 in the presence of MAO related to the polymerization yield. The maximum polymerization yield was observed with regard to the relative maximum value of the absorption intensity at λmax = 410 nm with the [Al]/[Ti] ratio (500). From observation for polymorphism of the final products via differential scanning calorimetric analysis (DSC), the thermally unstable β-form seemed to be produced by the CpTiCl3/MAO system independent of the MAO concentration, the Ti(OC4H9)4/MAO system produced a thermally stable α-form in the low MAO concentration (up to 100 of the [Al]/[Ti] ratio), and a mixture of α- and/or β-forms over 200 of the [Al]/[Ti] ratio under our experimental conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1733-1741, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure effect in the coupling reactions of polymeric organolithium compounds using chlorosilanes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1743-1753 
    Details
    ISSN: 0887-624X
    Keywords: coupling reaction ; living polymer ; microstructure ; coupling yield ; 1,4-enchainment ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The most important variable affecting the yield in the coupling reactions of polymeric organolithium compounds with chlorosilane compounds has been investigated through size-exclusion chromatographic (SEC) analysis. The coupling reaction of poly(styryl)lithium with dichlorodimethylsilane as a silane-coupling agent provided 44 wt % of the coupling yield. The coupling yield, depending on the chain end reactivity of active polymers, was not greatly affected. The addition of a Lewis base such as N,N,N′,N′-tetramethylethylenediamine (TMEDA) even after complete polymerization of the dienes in hydrocarbon seems to affect the coupling reaction, resulting in decreasing the yield. The 1,2- or 3,4-enchain contents in the polydiene backbones affected the reduction of the linking efficiency in the coupling of the poly(dienyl)lithiums with chlorosilanes as the linking agent. The linking yields of the active polymers including over 75 mol % of 1,2- or 3,4-enchainment on the polydiene segment were below 20 wt %. The linking yields exhibited a dependence not only on the steric requirement of the chain end, but also the microstructure of the polydiene segment. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1743-1753, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Melting point depression and phase behavior of poly(ether-sulfone) and poly(ethylene oxide) blends: Equation-of-state theory approach (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 2 (1993), S. 37-54 
    Details
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Melting-point depression in miscible polymer blends is interpreted with Flory-Prigogine's equation-of-state theory (FP theory) and Sanchez-Lacombe's lattice fluid theory (LF theory). The equations for equilibrium melting point depression in polymer mixtures are proposed from both the FP and LF theories. For miscible poly(ether-sulfone) (PES)/poly(ethylene oxide) (PEO) blends, the proposed equations are tested. The interaction parameters, X12 in FP theory and ζ12 in LF theory, can be determined with these equations. The theoretically predicted equilibrium melting-point depression is subdivided into three terms, namely, the equation-of-state, the entropy and the contact interaction terms. When the estimated interaction parameters are converted to the heat of mixing by use of both theories, the composition dependence of the heat of mixing can be properly predicted. Using the interaction parameters obtained from the melting-point depression in PES/PEO blends, the spinodal curves are simulated from both the FP and LF theories.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1993.040020104
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  • 4
    Electronic Resource
    Electronic Resource
    Separation of water/ethanol mixture through poly(acrylonitrile-co-acrylic acid)/poly(ethylene oxide) membranes by pervaporation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 529-535 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The separation of water/ethanol mixtures was investigated by poly(acrylonitrile-co-acrylic acid) and by poly(acrylonitrile-co-acrylic acid)/poly(ethylene oxide) blend membranes. The flux increased with the content of acrylic acid in copolymers and the selectivity remained constant. The marked increase of the selectivity was observed for blend membranes of a certain blend ratio, suggesting that the two polymers are partially miscible. Poly(ethylene oxide) in blends was thought to act as a plasticizer as well as a preferentially water absorbing and diffusing component. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510316
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  • 5
    Electronic Resource
    Electronic Resource
    Modified free-volume model for pervaporation of water/ethanol mixtures through membranes containing hydrophilic groups or ions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 63-76 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The free-volume model for pervaporation has been modified by considering the polar path, in order to apply the model to membranes containing hydrophilic groups. The free-volume parameters were determined by inverse gas chromatography. For the polyacrylonitrile (PAN) membrane, the transport mechanism could be analyzed only by the free-volume model; however, for a membrane containing a hydrophilic moiety, the transport properties could be interpreted by the modified model. In water/ethanol mixtures, ethanol transports through the membrane matrix, while water permeates through the polar pathways consisting of polar groups or ions and water molecules as well as through the membrane matrix. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070570107
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of the viscosity ratio of dispersed phase to matrix on the rheological, morphological, and mechanical properties of polymer blends containing a LCP (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 443-452 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of the viscosity ratio of the dispersed LCP phase to the polystyrene/poly(phenylene oxide) (PS/PPO) thermoplastic matrix on the rheological, morphological, and resultant mechanical properties of the LCP blends was investigated. The viscosity of PS/PPO is largely dependent on the blend composition, so that different levels of viscosity ratios of dispersed LCP phase to PS/PPO thermoplastic matrix are obtained by using PS/PPO premixtures of different blend ratios as a thermoplastic matrix. When the viscosity of the LCP dispersed phase is lower than that of the thermoplastic matrix, finely distributed fibril structure of LCP is obtained. Tensile modulus of injection molded specimens show a positive deviation from the additive rule when the viscosity ratio (ηLCP/ηmatrix) is smaller than unity. These improvements in tensile modulus are attributed to the formation of finely distributed LCP fibrils. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of solvent or hydrophilic polymer on the hydration melting behavior of polyacrylonitrile (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 457-462 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of solvent, DMF, and hydrophilic polymer on the hydration melting behavior of Tae Kwang polyacrylonitrile-based copolymer (T-PAN) was investigated by DSC measurement. The melting temperature (Tm) of T-PAN was sharply lowered by incorporating water under autogenous pressure, but leveled off above a critical water content: 23 wt %. However, an additional incorporation of DMF into the hydrated T-PAN further lowered the Tm, even above the critical water content. On the other hand, addition of water-soluble poly(acrylic acid), poly(vinyl alcohol), and poly(ethylene glycol) or water-swellable starch to the hydrated PAN slightly raised the Tm. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540405
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  • 8
    Electronic Resource
    Electronic Resource
    Segmented block copolyetheramides based on nylon 6 and polyoxypropylene. I. Synthesis and characterization (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 585-591 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Various segmented block copolyetheramides based on nylon 6 and polyoxypropylene (POP) were synthesized by melt polymerization of caprolactam (CPL) and polyoxypropylene diamines (POPD) as a function of the size and content of POPD. As the content of POPD in the feed increased, the IR absorption band at 1110 cm-1 increased. The 1H-NMR analysis indicated that peaks characteristic of methylene groups in POP unit appeared at 1.2, 3.6, and 3.8 ppm. The compositions of the hard and soft segments in the block copolymer were determined from the NMR data. The POP content in copolymer was higher than that in the feed due to the removal of unreacted CPL by water extraction. The average block lengths of the hard and soft segments were calculated from molecular weights and copolymer compositions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540509
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal stability of polyacrylonitrile in the melt formed by hydration (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1793-1798 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Differential scanning calorimetry (DSC) and intrinsic viscosity measurement have been used to investigate the thermal stability of PAN-based copolymer in the melt formed by hydration. Samples containing various water contents were annealed at temperatures between 160 and 180°C for periods up to 60 min. The melting point (Tm) and crystallization temperature (Tc) increased with annealing time, irrespective of annealing temperature and water content. The increase in Tm with annealing time was interpreted in terms of thermodynamic parameters. The decrease in the heat of fusion (ΔHf) with the increase of annealing time implies that the number of nitrile groups is reduced during annealing in the melt. The decrease in the entropy of fusion (ΔSf) calculated from Tm and ΔHf suggests that the polymer chain becomes more rigid as the annealing time (or temperature) increases; however, the intrinsic viscosity does not increase during annealing. From both thermodynamic analysis and intrinsic viscosity, it is concluded that the increase in Tm is caused by chain rigidity mainly due to the intramolecular cyclization of nitrile groups. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070461010
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  • 10
    Electronic Resource
    Electronic Resource
    The morphology and mechanical properties of phenoxy/liquid crystalline polymer blends and the effect of transesterification (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 561-569 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Morphological, rheological, and mechanical properties of poly(hydroxy ether of bisphenol A) (phenoxy) and a Vectra liquid crystalline copolyester (LCP) blends were investigated. Scanning electron micrographs of fracture surfaces of injection-molded samples show that the LCP forms an elongated fibrous dispersion in the phenoxy matrix. As the mixing time increases, the tensile strength and modulus increase while the elongation at break remains almost constant. These improvements are attributed to the formation of LCP-grafted phenoxy by the interchange reaction between phenoxy and LCP. The interchange reaction was identified by DSC, a rheometer, and a FTIR spectrometer. The graft copolymer gives better adhesion between the two phases and thus improves mechanical properties of the blends. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550403
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