Shape and Color Switchable Block Copolymer Particles by Temperature and pH Dual Responses.

Herein, we report a simple and robust strategy for preparing dual-responsive shape-switchable block copolymer (BCP) particles, which respond to subtle temperature and pH changes near physiological conditions (i.e., human body temperature and neutral pH). The shape transition of polystyrene- b-poly(4-vinylpyridine) BCP particles between lens and football shapes occurs in very narrow temperature and pH ranges: no temperature-based transition for pH 6.0, 40-50 °C transition for pH 6.5, and 25-35 °C for pH 7.0. To achieve these shape transitions, temperature/pH-responsive polymer surfactants of poly( N-(2-(diethylamino)ethyl)acrylamide- r- N-isopropylacrylamide) are designed to induce dramatic changes in relative solubility and their location in response to temperature and pH changes near physiological conditions. In addition, the BCP particles exhibit reversible shape-transforming behavior according to orthogonal temperature and pH changes. Colorimetric measurements of temperature and pH changes are enabled by shape-transforming properties combined with selective positioning of dyes, suggesting promising potential for these particles in clinical and biomedical applications.