Synthesis and Characterization of Novel Poly(N-isopropylacrylamide-co-N,N′-dimethylaminoethyl methacrylate sulfate) Hydrogels

Poly( N -isopropylacrylamide-co- N, N ′-dimethylaminoethyl methacrylate sulfate) [P(NIPAM-co-DMAEMASA)] was prepared from N -isopropylacrylamide (NIPAM) and N, N -dimethylaminoethyl methacrylate sulfate (DMAEMASA) monomers, and its properties were compared with those of poly( N -isopropylacrylamide-co- N, N ′-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMAEMA)]. The copolymers were characterized by swelling measurements in distilled water (10−40 °C) and buffer solutions ( I = 0.1 M, pH = 2.2−10.0), FTIR, DSC, and SEM methods. The ESV’s of the NIPAM-DMAEMASA copolymers in distilled water were 5 times higher than those of P(NIPAM-co-DMAEMA); they decreased with an increase in comonomer (DMAEMASA/DMAEMA) content for both copolymers. While NIPAM-DMAEMASA copolymers did not display any phase transition with temperature, the LCST of the NIPAM-DMAEMA copolymer was determined as 20 °C. Both copolymers displayed a phase transition at pH = 5.0, but the pH of the phase transition for NIPAM-DMAEMA gels shifted to 7.0 with increased DMAEMA content. Glass transition temperatures of NIPAM copolymers did not change with the type and content of comonomer.