Reversible micelle transfer between water and organic solvents in response to temperature was achieved using diblock copolymers with a hydro- and oleophobic segment and a hydro- and oleophilic segment. The block copolymers were synthesized precisely through the living cationic polymerization of a fluorine-containing vinyl ether (VE) and an oxyethylene-containing VE. The fluorine-containing segment formed the core of the micelles, both in water and in ethyl acetate, because of its insolubility in both solvents. An oxyethylene-containing segment, which formed the corona of the micelles, was soluble in both solvents but changed the affinity to water depending on temperature. Thus, a diblock copolymer with oxyethylene-side chains of appropriate length was reversibly transferred to ethyl acetate at higher temperature and to water at lower temperature.
Precision synthesis of a block copolymer composed of poly(2-methoxyethyl vinyl ether) and poly(p-tert-butoxystyrene) segments as thermosensitive and film-forming segments, respectively, was achieved by sequential living cationic polymerization in the presence of a weak Lewis base and a proton trap reagent. The choice of Lewis acid catalysts and appropriate polymerization temperature were crucial for the successful synthesis of a well-defined block copolymer. The obtained block copolymer had a very narrow molecular weight distribution (Mw/Mn < 1.1) and formed free-standing films. The surface wettability of the film by water was examined through static contact angle measurements. The wettability sharply decreased around 60°C upon raising the temperature. It should be noted that this sensitive transition is completely reversible during repeated cycling. Furthermore, the thermosensitive behavior was controlled by the film preparation conditions, such as casting solvent and solvent annealing.