Cononsolvency-Induced Microphase Separation of Double Hydrophilic Poly(2-ethyl-2-oxazoline)–Polycarboxybetaine Diblock Copolymers in Water–Ethanol Mixtures

Abstract

The cononsolvency-induced solvent composition-specific self-assembly of a double hydrophilic diblock copolymer comprising a cononsolvency active poly­(carboxybetaine methacrylate) (PCB2) and inactive poly­(2-ethyl-2-oxazoline) (PEtOx) (PEtOx n -b-PCB2 m ) was investigated. PEtOx n -b-PCB2 m dissolved in water and ethanol but aggregated in their mixtures with a specific ethanol volume fraction (f EtOH) range (0.76–0.96) owing to the cononsolvency of PCB2 chains. PEtOx n -b-PCB2 m produced well-ordered mesoscopic lattice structures in water–ethanol mixed solvents, and their morphologies and lattice distortion depended on f EtOH and the polymer concentration. PEtOx n -b-PCB2 m produced the most ordered lattice structure at f EtOH = 0.5–0.6, where PCB2 chains aggregated moderately. The controlled microphase separation, morphology transition, and collapse of biocompatible mesophases can pave the way for the design of stimuli-responsive molecular compartments.