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  • 1
    Electronic Resource
    Electronic Resource
    Infinite Dilution Diffusion Coefficients of Several Aromatic Hydrocarbons in Octane and 2,2,4-Trimethylpentane (1995)
    s.l. : American Chemical Society
    Journal of chemical & engineering data 40 (1995), S. 1053-1055 
    Details
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/je00021a004
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  • 2
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the conformational entropy of polymer chains (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1672-1674 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Monte Carlo method, namely, the "statistical counting method'' (SCM) has been proposed for simulating the conformational entropy of a single free or confined linear self-avoiding random walk chains on the simple cubic lattice. For a free linear chain with length 1081, it is found from the calculated results of 100 groups of 104 samplings that the maximum and the minimum values of the conformational entropy are 1670.2 and 1660.3, respectively, the deviations from the average value 1663.8 are only +0.39% and −0.2%. In the range of chain length 8–20 the calculated entropy data are found to be in agreement with their precise values obtained by M. F. Sykes, et al. [J. Phys. A 5, 653 (1972)] with deviation less than 0.05%. In the range of chain lengths up to 27 confined in a cube of side length 2, the entropy data are also consistent with their precise values obtained from the direct counting of conformation number with the deviations less than 0.6%. For a long chain with lengths up to 2101, the calculated entropy data have confirmed the prediction by the renormalization group theory very well and the deviation is less than 0.8%. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470753
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of Pauci-Chain Polystyrene Microlatex Particles Prepared by Chemical Initiator (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 1592-1597 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00109a035
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  • 4
    Electronic Resource
    Electronic Resource
    Subglass-transition-temperature annealing of poly(ethylene terephthalate) studied by FTIR (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 783-788 
    Details
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; sub-Tg ; annealing ; conformation ; infrared spectra ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using FTIR spectroscopy we have examined conformational changes in the quenched and slowly cooled amorphous PET films during physical aging process. It was observed that the amount of trans conformers for quenched sample decreased upon sub-Tg annealing. For the slowly cooled sample that corresponds to a state closer to equilibrium, the amount of trans conformers hardly decreased, but increased gradually during sub-Tg annealing process. The conformational populations of these two samples tend to be identical with annealing time. These results demonstrate that sub-Tg annealing will lead to closer interchain packing and result in the formation of new cohesional entanglements along the chains. In situ FTIR studies on the conformational changes of these samples were also carried out during heating up of the sample through the glass transition region. The results showed that incremental changes of the amount of trans conformers in Samples Q and SC were gradual, while an abrupt change of trans conformers occurred in the sub-Tg annealed samples. These results were in agreement with the formation of the interchain cohesional entanglement due to sub-Tg annealing. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 783-788, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Length of chain segment motion needed for crystallization (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 19-23 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The length of chain segment motion needed for the crystallization of guttapercha from rubbery state was found to be around 180 C—C bonds of the backbone chain. Thus, the crystallization process from the rubbery state or from the melt is not through chain folding, and the solidification model is a more appropriate physical picture of the process.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030160104
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  • 6
    Electronic Resource
    Electronic Resource
    Morphological observations of single-chain glassy polystyrene by means of tapping mode atomic force microscopy (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 2165-2174 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Tapping mode atomic force microscopy has been used to observe single-chain polystyrene (SCPS) particles sprayed with an atomizer onto freshly cleaved mica surfaces from very dilute solutions of a polydisperse polystyrene sample in good solvents, methylene cloride and benzene, and in poor solvents, CH2Cl2/MeOH 3/1.2 v/v and CH2Cl2/MeOH 3/1.3 v/v. The SCPS particles possess a definite morphology irrespective of the molecular weight but depending on the solvent. The morphology was found to change with time during drying after spraying and to be very sensitive to solvent environment and external forces exerted by the tip of the scanning probe. The particles became oriented due to probe-tip-particle interaction during probe scanning. Only qualitative comparison were made for the sizes of the observed images owing to the polydispersity and irregular shape of the particles and uncertainties about the tip convolution effects on the lateral dimensions. Only in the case of spraying the solution in poor solvents particles close to the shape of spheres were observed. In other cases the heights of the particles sprayed were an order of magnitude smaller than the lateral dimensions. AFM imaging has been applied to observe changes in morphology of SCPS particles sprayed from solutions after freeze thaw cycling. The results do not support the idea of cryogenic degradation of PS but the morphology of PS in solution changed to a smaller coil size during cryogenic freezing which persisted after being brought back to room temperature. When the freeze thaw cycled solution was heated to 100°C and then cooled to room temperature the coil size increased with a resulting morphology similar to the morphology observed before freeze thaw cycling.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021970708
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  • 7
    Electronic Resource
    Electronic Resource
    Viscometric investigation of intramolecular hydrogen bonding cohesional entanglement in extremely dilute aqueous solution of poly vinyl alcohol (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2421-2427 
    Details
    ISSN: 0887-6266
    Keywords: intramolecular hydrogen bonding ; entanglement ; viscosity ; solution ; polyvinyl alcohol ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An investigation of influence of cryogenic treatment on extremely dilute aqueous solution of poly(vinyl alcohol) (PVA) was performed by viscometry. The solution was frozen in liquid nitrogen or in a freezer at -25°C, then thawed at ambient temperature and concentrated by evacuation. The viscosity of the solution was measured using the dilute method. The experimental results indicated that the viscosity of the solution is related to N, the times of the freezing and thawing cycle, and the temperature for freezing. Undergoing a treatment of freezing and thawing, the viscosity of the solution is decreased, while it can be recovered the value of before the treatment as the solution had been heated at a high temperature. Thus, a conclusion may be obtained; that is, for an extremely dilute aqueous solution of PVA, which concentration is below Cgel, threshold concentration for gelation, an intramolecular hydrogen bonding cohesional entanglement can be formed by freezing as N 〈 5. However, in the case of N 〉 5, it not only formed an intramolecular hydrogen bonding but also produced an intermolecular hydrogen bonding. At the same time, the abnormal behavior of reduced viscosity of the solution in extremely dilute concentration region has been explained. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2421-2427, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of physical ageing on conformational changes of poly(ethylene terephthalate) in the glass transition region (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 1485-1493 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In-situ FTIR studies on the conformational changes of poly(ethylene terephthalate) (PET) films with different thermal histories, i. e., quenched from the melt and sub-Tg annealed at different temperatures, were carried out while increasing the temperature through the glass transition region. The temperature dependencies of the infra-red spectra showed that incremental changes of the population of trans conformers in the quenched sample are gradual, while rather abrupt changes occur in the sub-Tg annealed samples. The magnitude and temperature of the abrupt changes of trans conformers were related with the temperature of sub-Tg annealing. An energy difference of 28.6 J/g between the trans and gauche conformational states was measured by the infra-red spectroscopic method. The energy absorbed during the abrupt conformational change represents only part of the energy of the endothermic peak observed by differential scanning calorimetry. The results are explained in terms of the formation of new cohesional entanglements during sub-Tg annealing.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021970425
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of solution concentration on the gelation of aqueous polyvinyl alcohol solution (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1731-1735 
    Details
    ISSN: 0887-6266
    Keywords: polymer solution ; physical gel ; gelation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The concentration dependence of cryogenic gelation for aqueous solution of poly(vinyl alcohol) was studied by measuring the apparent gel fraction G and the swelling ratio Q of the gel formed by freezing and thawing. It was found that for the gelation process there were three distinct regions of solution concentration bounded by two concentrations Cgel and Cgel*. The gel started to form at C = Cgel, while no visible gel could be detected even upon repeated freezing and thawing of the extremely dilute solutions of C 〈 Cgel. The entire solution was gelatinized as a whole in the high concentration region of C 〉 Cgel*. In the intermediate concentration region, Cgel 〈 C 〈 Cgel*, which covers three orders of magnitude in concentration, gel and sol phases coexist. Both concentration dependencies of G and Q show two branches jointed at a concentration very close to the overlap concentration C*. The curve of GċQ versus C shows a sharp cusp. In case the sharp cusp concentration is really the value of C*, gelation offers a precise method to determine the overlap concentration. ©1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331204
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the crystal nucleation behavior of a single chain touching a substrate surface (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 75-80 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular dynamics simulation has been used in exploring the crystal nucleation behaviour of a single chain touching a substrate surface. It shows that a polyethylene chain (980 CH2) changed its overall shape from an isotropic coil to an oriented one in the case of touching a substrate surface of amorphous carbons at 300 K. Most repeats of the chain were aligned and ordered in a zigzag package. Surprisingly, the direction of the package is not parallel to the plane of the substrate, but almost perpendicular to it. This is in accordance with experimental observations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1996.040050105
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