MD Simulation Study of the Influence of Branch Content on Crystallization of Branched Polyethylene Chains with Uniform Branch Distribution

Abstract

Linear low-density polyethylene (LLDPE) chains with different levels of branch content (BC), ranging from 10 to 80 branches/1000 C, distributed uniformly along the chain were simulated in vacuum at a temperature of 350 K. The influence of BC on the relaxation and crystallization of LLDPE chains was studied. The collapse of the branched chains was found to occur via a local followed by a global collapse mechanism with branches acting as nucleation points for the collapse of the molecule leading to a faster collapse of chains with higher BC. The trans population was found to be dominant at all branch contents; however, it decreases with increasing BC. Increasing BC was found to decrease order and to strongly influence chain conformation. Chain conformation undergoes a transition from lamellar to a more random coil-like structure near a critical BC of 50 branches/1000 C. Branches were observed to be excluded from the lamella and to self assemble at high BC. This work also provides insight into the conformation adopted during the coil-globule transition experienced by a single chain in an infinitely dilute solution much below the Θ temperature.