  Using molecular dynamics simulations we examine the dynamics of a family of
model polymers with varying chain length and torsional potential barriers. We
focus on features of the dynamics of polymers that are seen experimentally but
absent in simulations of freely rotating and freely jointed chains. The reduced
effect of volume on the segmental dynamics with increasing chain length, a
capacity for pressure densification, and the deviation from constant
Johari-Goldstein relaxation time at constant segmental relaxation time all have
a common origin - torsional rigidity, and these effects become increasingly
apparent for more rigid chains.
