Thermoresponsive aggregation behavior of triterpene-poly(ethylene oxide) conjugates in water

Abstract

Bioconjugate amphiphiles comprising triterpene and poly(ethylene oxide) (PEO) were studied according to their thermoresponsive aggregation behavior (LCST) in water. Cholesteryl-PEO (CE) and betulinyl-PEO (BE) comprising <70 wt% PEO precipitated from water upon heating. CE, but not BE, solutions contained nanoscopic aggregates at room temperature causing different thermoprecipitation behaviors. Solutions containing 5 wt% solutions of BE with short PEO chains demonstrated dual thermoresponsive behavior, precipitating at high temperature and forming hydrogel at low temperature. A BE multiblock copolymer was found to form large aggregates, presumably vesicles, in water. Results suggest that the solution properties of triterpene-PEO amphiphiles can be controlled by the chemical composition and structure.