Cloud Points in Aqueous Poly(N-isopropylacrylamide) Solutions

The cloud point was determined for aqueous solutions of four kinds of poly(N-isopropylacrylamide) samples synthesized by radical polymerization in methanol, tert-butanol, benzene, and 1,4-dioxane by the use of azobis(isobutyronitrile) as an initiator, in the range of the weight fraction of the sample from 0.5 to 10%. It has then been found that the cloud points so determined for the samples synthesized in benzene and 1,4-dioxane are definitely lower than those for the samples synthesized in methanol and tert-butanol, although all the samples have almost the same stereochemical composition and the same end group. The observed deviation may be regarded as arising from the difference in the primary structure between the samples.