Polydispersity Effect on Phase Behavior of Diblock Copolymer

Effect of polydispersity on phase behavior of diblock copolymer was studied by Monte Carlo simulation. In order to evaluate the polydispersity effect, block copolymer blends including three different components were utilized as models in the simulation. By controlling the weight fractions of the component in copolymer blend, the influence of two different types of polydispersity effects (i. e. overall polydispersity effect and single block polydispersity effect, respectively) on order-disorder transition(ODT), conformations, and chain size of polymers were investigated. The results show that the increasing of index of polydispersity(PDI) can cause the ODT temperature slightly shifts to a lower temperature region. And it can also induce the increasing of the spacing thickness of the newly formed lamellar structure. Based on microscopic conformation analysis, polymer chains tend to stretch more at larger PDIs, which reveals the decreasing of accumulation degree of polymer chains. Therefore, the inhibition effect on fluctuation diminishes and the disordered phase shifts to the lower temperature region.