Effects of Surfactants on Phase Transition of Poly(N-isopropylacrylamide) and Poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate)

Abstract

The effect of surfactants on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate) (P(NIPAM-co-DMAEMA)) was extensively investigated by a turbidometry. When the concentration of cetyltrimethyl ammoniumchloride (CTAC) increased from 0.01 to 0.32%, the cloud point of PNIPAM increased from 32 to 38.5°C. When the concentration of sodium dodecyl sulfate (SDS) increased from 0.01 to 0.08%, the cloud point increased from 32.5 to 38°C. The cloud points with SDS were higher than the values obtained with CTAC. In addition, SDS suppressed the temperature sensitivity much more effectively than CTAC did. The adsorption of the ionic surfactants (CTAC, SDS) on the polymer chains may account for the increase in the cloud point. On the other hand, Tween 20 had little effect on the cloud point and the temperature sensitivity of the homopolymer, possible because it is nonionic. The effect of surfactants on the phase transition of P(NIPAM-co-DMAEMA) exhibited a trend similar to the effect on the phase transition of PNIPAM.