Biomimetic pegylated polypeptoids with thermoresponsive properties

Smart polymeric materials have received extensive attention for various applications. Here, we reported a facile and efficient approach to prepare a class of pegylated polypeptoids by a combination of ringopening polymerization (ROP) and post-modification strategy. Three different initiators were involved to mediate the polymerization of the monomers. Unlike the previously reported pegylated polypeptoids, the obtained polypeptoids show completely reversible thermoresponsive behaviors in aqueous solution after 8 heating and cooling cycles. In addition, the phase transition of the polypeptoid solutions can be very sharp (Delta T < 5 degrees C), which is comparable to poly(N-isopropylacrylamide) (PNIPAM). The influence of temperature on solution properties of the polypeptoids has been systematically studied. The clouding points (CPs) of the polypeptoids are highly tunable depending on the degree of polymerization (DP), the side-chain length, and the polymer concentration. We demonstrate that the thermoresponsive property of the polypeptoid may possibly arise from the incorporation of thioether groups and the branched molecular architecure of side chains. These features enable the pegylated polypeptoids potential candidates for next generation of smart polymeric materials. (C) 2018 Elsevier Ltd. All rights reserved.