Enlarged Stable Phase Region of Hybrid Lamella-sphere Phase Enabled by A1B1A2(B2)m Branched Tetrablock Copolymer

Abstract

Hybrid nanostructures possess a great potential for application in advanced nanotechnologies due to the anisotropic properties from different nanophases. Our previous work demonstrated that a linear A1B1A2B2 tetrablock copolymer of symmetric overall volume fraction can self-assemble into a hybrid lamella-sphere (LS) structure by tuning the relative length of the two A-blocks through self-consistent field theory (SCFT), where the spherical and the lamellar domains are mainly composed of the long A1- and short A2-blocks, respectively. However, the phase region of LS is limited. In order to expand the stable region of LS, we change the linear A1B1A2B2 copolymer to a branched A1B1A2(B2)m copolymer resulting in an increase of the local spontaneous curvature between A2- and B2-blocks. We examine the impact of the branching number m of B2-block on the stable region of LS in the phase diagram with respect to fA1 and XN for fixed fB=0.5 and fB1=0.26, and find that m=2 expands the LS region significantly in contrast to the linear architecture. On the other hand, the stability window of LS does not change notably when m=2 is increased to 3 in our calculated parameter space.