Effect of monomer sequence on structural and dynamic properties of ethylene-propylene copolymer melts

Monte-Carlo simulation of the coarse-grained model was applied to investigate the structures and dynamics of ethylene-propylene copolymer (EPC) melts with different monomer compositions and monomer sequences. The chain dynamics are strongly dependent on the ethylene fraction (P-E) in EPC chains. The tendency of molecular mobility for EPC is faster for the block-like sequences than other patterns. The dynamics of EPC with different monomer sequences were analyzed to correlate with both intra- (the characteristic ratio and the radius of gyration) and intermolecular contribution (the intermolecular pair correlation function). At low to intermediate ethylene fraction (P-E = 0.25 and 0.5), the effect of intermolecular interaction plays a more dominant role than that of intramolecular contribution. At a higher ethylene fraction (P-E = 0.75), the intermolecular packing and chain dimension are not significantly different as a result of a large fraction of more mobile ethylene beads, and the effect of consecutive monomer sequence is likely to affect the chain mobility.