Modeling of the polyethylene and poly(L-lactide) triblock copolymer: a dissipative particle dynamics study

Dissipative particle dynamics (DPD), a mesoscopic simulation approach, has been used to investigate the effect of the arrangement of the microstructure and the effect of the volume fraction on the structural properties of the immiscible polyethylene (PE)/poly(L-lactide) (PLLA) polymer in the triblock copolymer system. In this work, the interaction parameter in DPD simulation, related to the Flory-Huggins interaction parameter chi, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics simulation. The immiscibility property of PE and PLLA polymers induces phase separation and exhibits different architectures at different volume fractions. In order to obtain the structural property, the radius of gyration and the end-to-end distance are used to observe the detailed arrangement of the triblock copolymer. The results show first that the relative volume fractions of PE and PLLA directly affect the bridge and loop fraction, and, second, that whether or not the arrangement is symmetrical or asymmetrical affects the equilibrium structure in the triblock copolymer system. Moreover, as the chain length of the component chains within the PE-PLLA-PE triblock copolymer increase, those component chains become softer; therefore, this directly affects the bridge and loop fraction.