A new thermoresponsive polymer of poly(N-acetoxylethyl acrylamide)

A new thermoresponsive polymer of poly(N-acetoxylethyl acrylamide) (PNAEAA) exhibiting a lower critical solution temperature in neutral water around 50 °C is synthesized by solution RAFT polymerization. In RAFT polymerization, the molecular weight of PNAEAA increases linearly with monomer conversion and Đ keeps at low values, confirming a controllable synthesis of PNAEAA. PNAEAA undergoes a reversible and sharp phase transition with almost no hysteresis at the phase transition temperature (PTT). The parameters, e.g., polymer concentration, degree of polymerization (DP), pH, salts, urea and phenol, affecting the PTT of PNAEAA are studied. Results demonstrate that the thermoresponsive phase transition of PNAEAA is different from its isomer of poly(N-acryloylglycine ethyl ester) (PNAGEE) and the popular poly(N-isopropylacrylamide) (PNIPAM). Due to the different PTTs of PNAEAA and PNIPAM, a doubly thermoresponsive block copolymer of poly(N-isopropyl acrylamide)-block-poly(N-acetoxylethyl acrylamide) (PNIPAM-b-PNAEAA) showing two PTTs is also synthesized. The thermoresponsive PNAEAA enriches the category of thermoresponsive polymers and is believed to have promising applications.