Dispersity Stabilized Complex Morphologies in AB Diblock Copolymers

Abstract

Block copolymers have the ability to self-assemble into a variety of complex microphase separated morphologies. Among the various attainable microdomain structures, complex morphologies such as bicontinuous gyroid (G) and hexagonally perforated lamellae (HPL) are highly desirable due to their inherent structural connectivity. For monodisperse AB diblocks, the G phase is thermodynamically stable, but its window of accessibility is small [1]. The HPL phase is even more difficult to obtain as it is determined to be metastable in nature [2]. It has been suggested by various calculations that such complex morphologies may be stabilized by increasing block dispersity [3-5]. In this study we prepared poly(styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers of varied dispersity (D = Mw / Mn) in both PS and PMMA blocks, then examined the formation of complex morphologies in these highly disperse diblock copolymers.