Local structure and dynamics of trans-polyisoprene oligomers

Mono- and polydisperse melts of oligomers (average length 10 monomers) of t rans-1,4-polyisoprene are simulated in foil atomistic detail. The force fie ld is developed by means of a mixture of ab initio quantum chemistry and an automatic generation of empirical parameters. Comparisons to NMR and scatt ering experiments validate the model. The local reorientation dynamics show s that for C-H vectors there is a two-stage process consisting of an initia l decay and a late-stage decorrelation originating from overall reorientati on. The atomistic model can be successfully mapped onto a simple model incl uding only beads for the monomers with bond springs and bond angle potentia ls. End-bridging Monte Carlo as an equilibration stage and molecular dynami cs as the subsequent simulation method together prove to be a useful method for polymer simulations.