Control of network structures in block copolymers

Abstract

We focus on the formation of the complex network microdomain morphologies ob block copolymers by different methods. Precise control of composition in polystyrene-block-polyisoprene (SI) was attained by anionic polymerization of styrene and isoprene or by addition of homopolymer into neat SI, and enabled us to form the Fddd structure. An ordered bicontinuous double-diamond (OBDD) morphology was found in Polystyrene-block-(poly-4-vinylphenyldimethylvinylsilane-graft-polyisoprene), a block-graft copolymer. The grafted polyisoprene chains induce the frustration of polystyrene chains and thus the effects of the specific interface are more dominant that those of the packing frustration in the formation of the morphology and the OBDD phase is thus stabilized. Ordered tricontinuous double-diamond morphology (OTDD) was formed in cast films of polystyrene-block-polyisoprene-block-polydimethylsiloxiane a triblock terpolymer from toluene solution, though the OTDD structure is not an equilibrium structure in triblock terpolymers. Two-step microphase separation occurs during solvent cast. Since the kinetic barrier of the transition from cylinder to gyroid is higher than that from cylinder to OTDD, the metastable OTDD was formed.