MD simulation of the influence of branch content on collapse and conformation of LLDPE chains crystallizing from highly dilute solutions

The influence of branch content (BC) on conformation of Ziegler-Natta linear-low density polyethylene (ZN-LLDPE) in dilute solutions was studied by molecular dynamics simulation. Octene LLDPE with different levels of BC distributed randomly along the chain mimicking ZN-LLDPE were simulated in vacuum at 400 and 500 K. Increasing BC was found to decrease chain folding and change chain conformation. Chain conformation undergoes transition from lamellar to a more random coil-like structure near a BC of 40 branches/1000 backbone carbons. Results are in agreement with recent experimental results of Zhang et al. [Polymer 42 (2001) 3067]. Extended chains with higher BC collapse faster and form more kinks than chains with lower BC with branches acting as nucleation points for the chain collapse. At high BC, branches are observed to self-assemble away from the backbone. (C) 2002 Published by Elsevier Science Ltd.