Simulation of Oligomeric Polyolefin Blend Phase Behavior

Understanding phase behavior of polyolefin blends is crucial for the design of many polymeric materials. A particular interesting problem is the irregular mixing behavior observed for certain polyolefin blends, where the binary interaction parameter chi is found to deviate significantly from the prediction of Flory-Huggins theory. The origin of this irregular mixing behavior is a matter of controversy. In this work, configurational-bias Monte Carlo simulations are carried out in various ensembles to investigate the solubility parameter, the Gibbs free energy of mixing, and the structure of unary systems and binary mixtures of oligomeric polyolefins represented by the TraPPE-UA force field. It is found that the simulations are consistent with the mixing behavior observed experimentally. In addition, the structural analysis provides some insights into the origin of the irregular mixing behavior.