A theoretical study on the inverted phase formation in diblock copolymer solutions

The inverted phase, in which the swollen minority block plus solvent forms the continuous microdomain, has been frequently observed in block copolymer (BCP)/preferential good solvent solutions in our previous experimental works. In this paper, self-consistent field theory is employed to study the formation of inverted phase in A-B BCP solutions. The parameters of both the BCP and solvent are studied. The results show that the characteristics of both the BCP and the solvent are responsible for the inverted phase formation. With the value of chi N-AB (chi(AB) is the Flory interaction parameter between A and B blocks and N is the degree of the polymerization), the preferential affinity of the solvent for the minority block, or the solvent monomer size increasing, the existence window of the inverted phases enlarges. Meanwhile, we analyze and discuss the formation of the inverted phase in terms of the enthalpy interaction and entropy contribution of the solvent and the results suggest that both of them play important roles in the formation of inverted phase and the comparative importance of the two items depends on the solvent molecular size. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769386]