EFFECTS OF SURFACTANTS ON THE PHASE-TRANSITION OF A HYDROPHOBIC POLYMER GEL

The effects of surfactants having various chemical structures on the p hase transition of poly(N-isopropylacrylamide) (NIPA) gel have been st udied. The phase transition temperature of NIPA gel, which is 34 degre es C in pure water, is elevated by several tens of degrees when a smal l amount of some surfactant is added to water. The transition temperat ure increases with surfactant concentration below the critical micelle concentration and is saturated at a certain temperature. The transiti on temperature strongly depends on the chemical structure in the hydro philic part as well as the length of the hydrophobic portion of the su rfactants. The transition temperature of the gel does not depend on th e counterion species. These hydrophile-lipophile balance (HLB).