Microphase separation in ABA triblock copolymer-based model conetworks in the bulk: Effect of loop formation

Abstract

This work estimates the free energy and domain size and predicts the phase diagram of microphase-separated model polymer conetworks, consisting of end-linked ABA triblock copolymers with cross-link points of relatively low functionality, in the strong segregation limit (highly incompatible A and B). Considering the case when these conetworks were prepared in the disordered state, their microphase separation is accompanied by extensive loop formation, with the fraction of loops depending on the morphology. The free energy of these conetworks is approximated using the expressions for linear block copolymers, modified to take into account the presence of loops whose free energy is estimated in two different approaches. The domain sizes in the conetwork system are found to be larger than those of the same morphologies in the linear system because of the reduction of the retractive force due to loop formation in the former system. The conetwork phase diagram is very sensitive to the expression used to describe the energy for loop formation. © 2006 Elsevier Ltd. All rights reserved.