Molecular dynamics simulation of polymer liquid and glass. III: Chain conformation

Molecular dynamics simulation has been performed with dense systems of alkane-like chain molecules subject to potentials restricting bond lengths, bond angles, and trans--gauche torsional angles and interacting with neighboring chains according to a truncated Lennard--Jones potential. The distributi...

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Bibliographic Details
Published inMacromolecules Vol. 22; no. 5; pp. 2259 - 2264
Main Authors RIGBY, D, ROE, R. J
Format Journal Article
LanguageEnglish
Published Washington, DC American Chemical Society 01.05.1989
Subjects
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Properties and characterization
Liquid state
Simulation
Conformational dynamics
Molecular model
Molecular dynamics
Polymer
Methylene polymer
Density
Glass transition temperature
Interaction energy
Glassy state
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Summary:Molecular dynamics simulation has been performed with dense systems of alkane-like chain molecules subject to potentials restricting bond lengths, bond angles, and trans--gauche torsional angles and interacting with neighboring chains according to a truncated Lennard--Jones potential. The distributions of bond lengths, bond angles, and torsional angles have been evaluated for a range of density varying by a factor of two. The overall population of trans conformer was found to be independent of density, in contrast to experimental results suggesting an enhancement of gauche conformer on densification of short-chain alkanes. A closer examination showed, however, that gauche enhancement occurred mainly among bonds at the chain ends and only at the high end of the density range studied. The nonbonded interaction energy was found to go through a minimum as the density was increased, and at densities higher than that corresponding to the potential energy minimum, the molecular shape was somewhat modified through reductions in the bond lengths, bond angles and the trans conformer populations. The conformer population over a temperature range sufficiently above the T sub g is well reproduced by the rotational isomeric state model, provided an "effective" trans--gauche energy difference, rather than the true value of the parameter used for the simulation, is used for the prediction. Graphs. 12 ref.--AA
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ISSN:0024-9297