Facile,Controlled,Room-Temperature RAFT Polymerization of N-Isopropylacrylamide

摘要

Poly(N-1sopropyl acrylamide)is a thermoresponsive polymer that has been widely investigated for drug delivery.Herein,we report conditions facilitating the controlled,room-temperature RAFT polymerization of N-1sopropylacrylamide(NIPAM).The key to success is the appropriate choice of both a suitable RAFT chain transfer agent(CTA)and initiating species.We show that the use of 2-dodecylsulfanylthiocarbonyl-sulfanyl-2-methyl propionic acid,a trithiocarbonate RAFT CTA,in conjunction with the room-temperature azo initiator 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile),in DMF,at 25 °C,yields conditions leading to NIPAM homopolymerizations which bear all of the characteristics of a controlled/'living" polymerization.We also demonstrate facile size exclusion chromatographic analysis of PNIPAM samples in DMF at 60 °C,directly on aliquots withdrawn during the polymerizations,which avoids the problems previously reported in the literature.