Molecular dynamics study of the conformation and dynamics of precisely branched polyethylene

The conformation and dynamics of precisely branched polyethylene, i.e., polyethylene molecules containing regularly spaced, short chain branches along its linear backbone, were studied using molecular dynamics simulation. Models with branch content varying from 0 to 47.6 branches per 1000 backbone carbons were studied over a temperature range of 273–550 K and under a constant pressure of 1 bar. Two types of models were built, one of which contained ethyl branches while the other contained hexyl branches. The results indicated that at a given temperature, the global orientation order parameter decreased almost linearly with increasing branch content up to a value of approximately 38.5 and increased considerably and unexpectedly at a branch content of 47.6. The order parameter was insensitive to the branch length except at high branch contents. The computed packing lengths and activation energy for diffusion are consistent with the above observations.