| In this work, a novel spacer block copolymer poly(N-isopropylacrylamide)-oligolactide-poly(ethylene glycol)-oligolactide-poly(N-isopropylacrylamide) (PNIPAAm-OLA-PEG-OLA-PNIPAAm) was synthesized and preliminarily characterized. Ring-opening polymerization of lactide, Ce(IV)-CH-OH redox initiated radical polymerization and direct polycondensation were employed in the synthetic approach for the spacer block copolymers. 1HNMR and FTIR spectra were used to characterize the spacer block copolymer. The inverted tube method, DSC and weight loss method were used to characterize the gelation, thermoreversibility and degradability, respectively, of hydrogel formed by spacer block copolymer. Based on available data, the average degradation rate of spacer copolymer (1 wt%/day) is much higher than that of PNIPAAm (0.03wt%/day).; As a minor part of this project, the minimum gelation concentration of PNIPAAm-PEG-PNIPAAm triblock copolymer with different block length of PEG was evaluated. It was found that if the composition of PEG is higher than 60% in the copolymer, no gelation occurs even if the temperature is above the LCST. |
