Local segmental dynamics of cis-1,4-polybutadiene, polypropylene and polyethylene terephthalate via molecular dynamics simulations

Abstract

The local segmental dynamics of cis-1,4-polybutadiene, polypropylene and polyethylene terephthalate have been investigated via isothermal-isobaric molecular dynamics simulations. The simulation pressure was 1 atm for all systems, with all simulation temperatures being at least 150 K above the polymer's glass transition temperature. The trajectories have been analysed via autocorrelation functions (ACFs) of chord vectors spanning different number of chain backbone bonds. Inverse Laplace transformations of these ACFs using the CONTIN algorithm afforded the corresponding distribution of relaxation times (DRTs) for the simulated dynamics. All DRTs illustrated a peak on fast timescales corresponding to short length scale segmental motion and a peak at longer timescales corresponding to longer length scale relaxations. A third peak, intermediate between the fast and slow processes, appears as the relaxation of chord vectors spanning increasing number of backbone bonds is considered. The temperature dependence of the relaxation dynamics is also investigated.

Keywords:

• molecular dynamics simulation
• polymer dynamics
• polybutadiene
• polypropylene
• polyethylene terephthalate

Acknowledgements

The authors gratefully thank the University of Leeds for providing a Ph.D. scholarship for Mr D. Whitley, and for provision of computing time on the Advanced Research Computer.