Reversible phase transformations in concentrated aqueous block copolymer solutions of poly(methyl acrylate)-b-poly(hydroxyethyl methacrylate-co- dimethylaminoethyl methacrylate)

We have synthesized and characterized concentrated aqueous block copolymer solutions made with a series of poly(methyl acrylate)-b-poly(hydroxyethyl methacrylate-co-dimethylaminoethyl methacrylate), PMA/PHD, diblock copolymers with varying dimethylaminoethyl methacrylate (DMAEMA) content. The concentrated aqueous block copolymer solution consisting of PMA/PHD with high DMAEMA content (75 mol %) exhibits reversible morphological transitions from disordered, interacting spherical micelles to hexagonally packed cylinders to alternating lamellae over a narrow temperature range (30°C) due to decreased hydrophilicity of DMAEMA units with increasing temperature. Between morphological transformations, the microstructures experience a decrease in characteristic spacing, reminiscent of a lower critical solution temperature-type response. By changing the DMAEMA content within the PHD block, we are able to tune the swelling characteristics of concentrated PMA/PHD solutions, as well as the range of morphologies accessible.