Effects of surfactants on cloud points in aqueous poly(N-isopropylacrylamide) solutions

The article examines effects of surfactants on cloud points in aqueous poly(N-isopropylacrylamide) solutions. The PNIPA sample M6 was the same as that used in the previous study of the cloud points in aqueous solutions. The cloud point in the aqueous solution of R3 without surfactant is higher than that of M6 because the hydrophilicity of the chain-end group is stronger for the former than for the latter, as pointed out in the previous study. For comparison, the literature data for aqueous PNIPA solutions with an addition of SDS are also shown in the figure by the dotted curve. The decrease in the cloud point observed for the solutions of the sample R3 with DTAC for a small cs is considered to arise because the cationic DTAC molecule bound to the negatively charged PNIPA chain end diminishes the hydrophilicity of the chain end.