Full-biodegradable polylactide-based thermoresponsive copolymer with a wide temperature range: Synthesis, characterization and thermoresponsive properties

Abstract

To develop a full-biodegradable thermoresponsive polymer with a wide temperature range, a hydrophilic, biodegradable and biocompatible thermoresponsive polymer having a polylactide backbone polymer and a side chain norbornene group was synthesized by ring-opening polymerization of a norbornene-functionalized lactide, followed by graft of backbone polymer with polyethylene glycol monomethyl ether (MPEG) and modification with isopropylamide (IPA), the latter of which critically influences the phase transition temperature of the copolymer. The effects of polymerization degree (DP), molecular weight of MPEG, the proportion of MPEG and IPA, and the concentration of polymer on the behaviors of the thermoresponsive polymer solution were systematically studied. The Cp ranged from 32 to 72 °C, and it was found that higher number of the MPEG moiety led to higher Cp, whereas the longer isopropylamide group resulted in lower Cp. It is noteworthy that with the unique characteristics, thermosensitivity at body temperature, biodegradability, and a well-defined copolymer structure, the developed thermoresponsive polymer is promising for biomedical applications as an essential material.