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Computer simulation study of bulk atactic polystyrene in the vicinity of the glass transition
Author(s) -
Lyulin Alexey V.,
de Groot J.J.,
Michels M.A.J.
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200390006
Subject(s) - polystyrene , legendre polynomials , glass transition , power law , autocorrelation , relaxation (psychology) , diffusion , materials science , thermodynamics , polymer , polymer chemistry , chemistry , physics , nuclear magnetic resonance , mathematics , quantum mechanics , psychology , social psychology , statistics
Molecular dynamics (MD) simulations of bulk atactic polystyrene have been performed in a temperature range from 100 K to 650 K at atmospheric pressure. Local translational mobility has been investigated by measuring the mean square translational displacements of monomers. The long‐time asymptotic slope of these dependencies is 0.54 at T > T g , showing Rouse behavior. Cross‐over from motion in the cage to Rouse like dynamics has been studied at T > T g with a characteristic crossover time follows a power law behavior as a function of T , as predicted by mode‐coupling theory (MCT). Local orientational mobility has been studied via the orientational autocorrelation functions, ACFs, (Legendre polynomials of the first and second, order) of both the main‐chain and side‐group bonds. The relaxation times of the orientational α ‐relaxation follow the same power law ( γ ∼2.9) as the characteristic translational diffusion time. Below T > T g both types of dynamics are described by the same activated law. The ACFs time‐distribution functions reveal the existence of activated local rearrangements already above T > T g .