Thermoresponsive Sulfone and Sulfoxide-Containing Polyacrylamides

Abstract

A series of thermoresponsive polyacrylamides containing sulfide, sulfone, or sulfoxide was successfully prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The thermal properties of polyacrylamides with sulfone or sulfoxide, which have not been studied before, were investigated for the first time. While poly[N-(2-(propylsulfonyl)ethyl)acrylamide] (P2SO2) with sulfone groups was water insoluble, poly[N-(2-(propylsulfinyl)ethyl)acrylamide] (P2SO) with sulfoxide groups was water soluble, indicating that the sulfoxide moiety is more hydrophilic than sulfone. By controlling the end of the polymer chain, we synthesized poly[N-(2-(ethylsulfonyl)ethyl)acrylamide] (P1SO2) and poly[N-(2-(butylsulfinyl)ethyl)acrylamide] (P3SO), which exhibit an lower critical solution temperature (LCST) in water around 24-26 degrees C. For adjusting a wide range of LCST, we synthesized the random copolymers by controlling the initial feed ratio of hydrophobic M2SO2 and hydrophilic M2SO. The amphiphilic block copolymers were also synthesized and assembled in water to yield the micelles. After adding H2O2 to this micellar solution, the hydrophobic block was oxidized and converted to a hydrophilic block, leading to the transformation of micelles to unimers.