The self-assembly and thermoresponsivity of poly(isoprene-b-methyl methacrylate) copolymers in non-polar solvents

Abstract

The self-assembly of a series of polyisoprene-block-poly(methyl methacrylate) (PI-b-PMMA) block copolymers, in aliphatic hydrocarbon solvents is reported for the first time. The block copolymers were prepared by a change of mechanism polymerisation (CHOMP) whereby living anionic polymerisation was used to prepare polyisoprene macroinitiators for ATRP (PI-Br), which was in turn used to polymerize MMA. The use of anionic polymerisation ensured optimal control over the molar mass and dispersity of the polyisoprene block, in a synthesis that is readily scaled-up, to enable the production of homologous series of block copolymers by varying only the molar mass of the PMMA block. The block copolymers were subsequently dispersed in n-decane or n-hexane, a selective solvent for the PI block, at high solids content of up to 30 wt%. Analysis of the resulting self-assembled nanostructures using DLS and TEM revealed that the block copolymers self-assemble into varying morphologies (spherical micelles, wormlike micelles or vesicles), dependent upon the molar mass and composition of the block copolymer, enabling the construction of a series of “phase-diagrams”. The resultant self-assembled structures were also found to be thermally responsive and, in some cases, underwent a change in morphology upon heating.