Precision Synthesis of Telechelic Poly(N-isopropylacrylamide) with Thiol-Termini for Construction of Homogeneous Network by Thiol-Ene End-Crosslinking

Abstract

End-crosslinking of telechelic prepolymers is attractive for the construction of homogeneous network structure toward the development of functional gel materials. In this paper, we demonstrated the usefulness of thiol-ene reaction as crosslinking reaction in combination with prepolymer synthesis by reversible addition-fragmentation chain transfer (RAFT) polymerization. Telechelic poly(N-isopropylacrylamide) (PNIPAAm) with thiol-termini was successfully prepared by RAFT polymerization followed by aminolysis reaction. The obtained prepolymers were employed for the reaction with four-armed vinyl compounds as a crosslinker in various solvent. It demonstrated that the polarity of the solvent strongly affected the molecular weight of the product and, in particular, a stable gel was obtained in methanol. The effect of the molecular weight and the feed concentration was also examined and it clarified that thiol-ene reaction gave an efficient crosslinking reaction. These results indicated that the combination of RAFT polymerization and thiol-ene reaction is suitable for end-crosslinking system.