NIPAM共聚物多孔水凝胶的光引发RAFT合成及其溶胀性能

SYNTHESIS OF POROUS HYDROGELS OF NIPAM COPOLYMER BY REVERSIBLE ADDITION FRAGMENTATION CHAIN TRANSFER PHOTOPOLYMERIZATION

采用光引发可逆加成-断裂链转移(RAFT)方法,在室温下先合成了链端含有三硫代碳酸酯基的大分子链转移剂聚(N,N'-二甲基丙烯酰胺)(PDMAM),然后与N-异丙基丙烯酰胺(NIPAM)、N,N'-二甲基双丙烯酰胺(BIS)交联共聚合,并通过聚乙二醇的制孔作用制得PNIPAM-g-PDMAM梳型/多孔水凝胶.采用FTIR、SEM等对水凝胶的结构进行了表征.讨论了水凝胶的制备原理,研究了接枝链和孔结构对水凝胶性能的影响.研究结果表明,PDMAM接枝链的存在提高了无孔水凝胶的溶胀比、退溶胀速率和最低临界溶解温度(LCST);孔结构能大幅度地提高无接枝链水凝胶的溶胀比和退溶胀速率,但未改变水凝胶的LCST;接枝链的存在并没有提高多孔水凝胶的溶胀比,但失水率较低.

The macro-CTA（chain transfer agent） of poly（N,N′-dimethylacrylamide）（PDMAM） containing trithiocarbonate groups was prepared by reversible addition fragmentation chain transfer（RAFT） polymerization.And then it reacted with N-isopropyl acrylamide（NIPAM） and N,N′-methylene-bisacylamide（BIS） to prepare the PNIPAM-g-PDMAM comb hydrogels with different lengths and contents of the grafted chains at 20℃.The porous comb hydrogels were prepare by using poly（ethylene glycol）（PEG4000） as a pore-forming agent.The structure of the hydrogels was characterized by FTIR（Fourier transform infrared spectrometer） and SEM（scanning electron microscope）.The photos of SEM indicated that comparing with conventional hydrogels,the porous comb dydrogles with loose structure had a distinctive porous characteristic.The mechanism of hydrogels synthesis and the effects of the grafted chains and porous structure on the properties of hydrogels were discussed.Experimental results showed that the grafted chains significantly affected the properties of nonporous hydrogels,including swelling ratio,deswelling rate and LCST（lower critical solution temperature）.Though the deswelling rate decreased,the grafted chains had no effect on the swelling ratio of the porous comb hydrogels.The formation of a porous structure has been shown to effectively enhance the deswelling rate of PNIPAM hydrogels without grafting chains,but it didn＇t change the LCST.