Shape-switching self-assembly of new diblock copolymers with UCST-type and LCST-type segments in water

Abstract

A dual thermosensitive behavior, i.e., self-assembly at both high and low temperatures, was achieved in water using vinyl ether block copolymers with imidazolium salt side-chains (exhibiting a UCST behavior) and oxyethylene side-chains (exhibiting an LCST behavior). The block copolymers were precisely prepared via living cationic polymerization in the presence of a weak Lewis base. They formed micelles at lower temperatures and vesicles at higher temperatures in water, as confirmed via UV-Vis spectroscopy, dynamic light scattering (DLS), static light scattering (SLS), variable temperature ¹H NMR, and fluorescence measurements using pyrene as a polarity-sensitive probe. Furthermore, concentrated aqueous solutions of the block copolymers underwent sol–gel transitions by either raising or lowering the temperature.