Interaction of poly(N-isopropylacrylamide) with perfluorooctanoic acid in aqueous solution

Interaction of poly(N-isopropylacrylamide) (PNIPAAM) with perfluorooctanoic acid (PFOA) was explored in aqueous solution. Increasing concentrations of PFOA were observed first to depress slightly the lower critical solution temperature (LCST) then to elevate it at concentrations greater than ca. 2.5 mM. At concentrations >ca. 3.5 mM, the LCST transition could not be detected by either microcalorimetry or cloud point measurements. PNIPAAM appeared to promote the micellization of PFOA. Pinacyanol dye experiments were ambiguous, but the aggregation concentration reported by surface tension measurements was clearly depressed upon addition of PNIPAAM.