HYDROPHOBIC INTERACTIONS OF POLY(N-ISOPROPYLACRYLAMIDE) WITH HYDROPHOBICALLY-MODIFIED POLY(SODIUM ACRYLATE) IN AQUEOUS-SOLUTION

The interactions between poly(N-isopropylacrylamide), PNIPAM, and poly (sodium acrylate) hydrophobically modified with octadecyl groups, HMPA , in aqueous solutions, were studied by using viscometry and turbidime try. The viscosity of mixtures of the two polymers, at 25 degrees C, m ay be several orders of magnitude higher than the viscosity of the cor responding mixtures of PNIPAM with the unmodified precursor poly(sodiu m acrylate). The higher the modification degree of the HMPA, the great er the viscosity enhancement. Furthermore, increasing the molar mass o f PNIPAM leads to a more pronounced viscosity increase. The elevation of the phase separation temperature of PNIPAM in the PNIPAM/HMPA mixtu res reveals, also, the development of interactions between the two pol ymers. These interactions are temperature-dependent, and a thermotkick ening behavior has been observed with increasing temperature.