Chain stretching effect on the morphology and kinetics of microphase separation of diblock copolymer under simple shear flow

Abstract

By incorporating the information of chain conformation into the free-energy calculation, the chain stretching effect on the morphology and kinetics of microphase separation of symmetric diblock copolymers under simple shear flow is investigated based on the time-dependent Ginzburg–Landau model. We first showed that the order–disorder transition (ODT) temperature increases with τ1γ̇, where τ1 is the Rouse terminal relaxation time and γ̇ is the shear rate. The simulation results show that τ1 and γ̇ play the central role in the morphology of microphase separated diblock copolymers. It is found that, for the case without chain stretching effect (τ1γ̇=0), perpendicular (with the lamella normal perpendicular to the flow direction and the velocity gradient direction) and parallel (with the lamella normal parallel to the velocity gradient direction) alignments are obtained for shallow and deep quenches, respectively. However, when the chain stretching effect is strong, i.e., high τ1γ̇, the undulated lamella transverse alignment (with the lamella normal parallel to the flow direction) can be observed. The processes of morphology forming and the lamella undulation are discussed based on the anisotropic growth of the correlation lengths.