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  • 1
    Electronic Resource
    Electronic Resource
    Crystal structure of the poly(ethylene oxide)-p-nitrophenol molecular complexPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 117-125 
    Details
    ISSN: 0959-8103
    Keywords: poly(ethylene oxide) ; p-nitrophenol ; molecular complexes ; crystal structure ; 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: A crystalline complex of poly(ethylene oxide) (PEO) and p-nitrophenol (PNP) was studied by differential scanning calorimetry, X-ray diffraction, and FTIR spectroscopy, The phase diagram of this system is characterized by a peritectic reaction, and reveals the formation of a new crystal form different from those of PEO, and PNP. The triclinic unit cell of the complex was determined from the X-ray diffraction patterns of differently oriented samples obtained by mechanical deformations or spherulitic crystallizations. Finally, the molecular packing and the conformation adopted by the PEO chains were determined by FTIR spectroscopy. Polarization measurements have shown that the aromatic rings are very nearly normal to the c parameter (chain axis) and that the 1-4 axes of PNP molecules are parallel to the a* reciprocal parameter (spherulitic growth direction). Finally, a new (t2 gt2 gt3) conformation is proposed for the PEO chains on the basis of a normal mode analysis and the calculation of the intramolecular energy.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360202
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  • 2
    Electronic Resource
    Electronic Resource
    An isochronous decoration method for measuring linear growth rates in polymer crystals (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 345-356 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The long spacing l of lamellar crystals of linear polyethylene increases with the crystallization temperature Tc. For low degrees of supercooling, the ratio Δl/ΔT is around 0.5 nm K-1 for PE single crystals obtained from solution in xylene. In the restricted situation where only conduction in the crystallization vessel is involved, a heat transfer analysis shows that about 20 s is needed to change by 5 K the crystallization temperature Tc in a cylindrical vessel of 1.5 mm radius. Such rapid change of the crystallization temperature induces a sharp increase or decrease of the thickness of the single crystals. After conventional shadowing with palladium-gold alloy, the steps on the crystals are observed by conventional bright-field electron microscopy. A pioneering work was performed in this way by Bassett and Keller in 1962. Our technique allows one to determine both the shape and the dimensions of single crystals or twinned crystals of polyethylene as a function of the time of crystallization, and therefore give the quasi-instantaneous growth rates at various times.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090240211
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental criterion for the crystallization regime in polymer crystals grown from dilute solution: Possible limitation due to fractionation (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 357-388 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By integration of equations previously derived by Frank, the growth rate of polymer crystals is shown to be dependent on their size, provided that the persistence length Lp or the kinetic length Lk = (2g/i)1/2 are significantly larger than the primary nucleus. A new method of decorating the fold surface (isochronous decoration) allows the measurement of the quasi-instantaneous growth rate of very small crystals obtained from dilute xylene solution of a sharp polyethylene fraction of moderate molecular weight (Mw = 17,000, Mw/Mn = 1.11). Although the theory predicts that the growth rate increases with the size of the crystals as long as its dimension is smaller than the persistence length and/or the kinetic length, such an increase is not observed experimentally with the sharp PE fraction presently used. Therefore it appears that both the kinetic length and the (hypothetical) persistence length are beyond the resolution limit of electron microscopy and that crystallization occurs in the polynucleation regime. An upper bound is obtained for the rate g at which a locally new layer spreads in two directions on the substrate. The rate is lower than is estimated by the commonly Accepted theories. These theories lead also to an abnormally high value for the lateral surface free energy. The possibility that the observed initial linearity of the growth-rate curve may results from a balance of opposite effects (an increase with the size of the crystals on the one hand, a decrease with decreasing concentration and possible fractionation on the other) is thoroughly examined and ruled out. In fact, it must be stressed that at the early beginning of crystallization, negligible parts of the sample are crystallized and it is only at the end of crystallization that these effects appear. The fall in the growth rate as crystallization ends is due neither to progressive exhaustion of the solution alone nor to a depletion of the concentration by diffusion for this sharp fraction of low-molecular-weight PE. The major effect comes from fractionation. This segregation of the various molecular weights is predicted on the basis of a simple model and is verified by gel permeation chromatography (GPC). The fact that in such a sharp fraction significant fractionation occurs precludes any accurate determination of the supercooling and of the concentration of the polymer actually crystallizing. Subtle differences in the molecular weight distributions may result in significant variation of the growth rate. In conclusion, as the data used in the first part of this work were obtained with only a small percentage of the dissolved polymer sample crystallized, the observed constancy of the growth rate does not result from mutual compensation of opposite effects, and our conclusions about crystallization regime, order of magnitude of the kinetic and persistence lengths, and value of the rate of lateral spreading of a secondary nucleus are well founded.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090240212
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  • 4
    Electronic Resource
    Electronic Resource
    Nucleation-controlled growth. Observations on (110) twinned polyethylene crystals (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 1183-1206 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The growth of (110) twinned crystals of a sharp fraction of linear polyethylene (Mw/Mn = 1.10) of moderate molecular weight (Mw = 17,000) is followed during crystallization by the isochronous decoration method. New morphological features are observed. The fast-growing tip of our laths presents, in addition to the two (100) facets usually observed, a possibly stable small reentrant (110) corner. This is a situation intermediate between the facies described by Dawson and Keller. Moreover, the slow tip of our laths presents various degrees of asymmetry with respect to the junction plane. A new characteristic length Ln = j/i is introduced to explain our morphological observations on (110) twinned crystals: j is the nucleation rate at a reentrant corner and i the nucleation rate on a smooth facet. Three linear growth rates Ghkl are calculated as a function of the length L of the face (hkl): Ghkl and Gĥkl or G′hkl are respectively the growth rates of a face bordered by two salient corners and by a reentrant corner. A distinction between Gĥkl and G′hkl is introduced to take into account the relative sizes of the two faces of the reentrant dihedral angle. The major points of the discussion concern (i) the stability of the (110) reentrant corner of the fast tip of the lath, (ii) the nearly constant shape of the twinned crystals, (iii) the effects of dislocations incorporated in the fast edge of the laths, and (iv) the various asymmetries observed in the slow tip of our laths. Theories of surface nucleation-controlled growth explain our various morphological observations on (110) twinned PE crystals, and growth usually proceeds in regime II.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090240601
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  • 5
    Electronic Resource
    Electronic Resource
    Test of the validity of the classical kinetic theory of polymer crystallization (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1275-1281 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Use of the accepted theories of polymer crystallization to interpret crystal growth rate data for a polyethylene fraction from dilute xylene solution leads to the conclusion that crystallization cannot proceed in either in regime I or regime II, nor in an intermediate regime. This apparent paradox means that the classical theory of polymer crystallization does not give the right order of magnitude of the rate of initiation and of the rate of spreading of a secondary nucleus.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280806
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  • 6
    Electronic Resource
    Electronic Resource
    Sur le mécanisme du gonflement des hauts polymères cristallins par les solvants (1967)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 109 (1967), S. 1-8 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei Raumtemperatur zu Filmen geformte und dann bei 110°C getemperte Polyäthylenproben wurden bei 85°C in Biphenyl gequollen und dann auf Raumtemp. abgeschreckt.Wie Klein- und Weitwinkel-Röntgenstreuungen zeigen, kristallisiert das Bisphenyl in flachen, etwa 10 Å dicken Kristallen zwischen den Polyäthylen-Einkristallen. Die gequollenen Proben sind fibrillär; sie lassen sich, wie die Elektronenbeugung zeigt, in Einkristalle aufspalten. Die Quellung beeinflußt die Textur der ursprünglichen Polyäthylenprobe nicht, welche eine b-Achsen-Orientierung hat. Die Orientierung der Bisphenylkristalle hängt nur von der Polyäthylentextur ab; Bisphenyl hat hier ebenfalls b-Achsen-Orientierung, die parallel zur Orientierung des Polyäthylens ist.
    Notes: Specimens of polyethylene laminated at room temperature and annealed at 110°C were swelled at 85°C by biphenyl and then quickly allowed to cool to room temperature.X-ray diffraction studies at large and low angles revealed that during the cooling process, biphenyl crystallizes into flat crystals of about 10 Å thickness, located between the polyethylene single crystals. The swelled specimens are friable. It is possible to desaggregate them into single crystals as shown by electron diffraction. Swelling does not affect the texture of the initial polyethylene specimens which is that of a b̄ axis fibre. Further more during the cooling process the orientation taken by the biphenyl crystals depends only on the polyethylene texture. The texture of biphenyl is that of a b̄ axis fibre parallel to the polyethylene fibre.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1967.021090101
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  • 7
    Electronic Resource
    Electronic Resource
    Limiting planes and thickness of lamellae in nearly single textured 6,6; 6,8; 6,10; 6,12 nylon samples (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 13 (1975), S. 249-257 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.130130501
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