The solvation and desolvation process in the course of coil-globule transition of aqueous poly (N-isopropylacrylamide) solution

The temperature dependence of the specific refractive index increment dn/dc of aqueous poly (N-isopropylacrylamide) solution in the range of 20 degree sC to 35 degreesC were determined by a differential refractometer. The meas ured dn/dc of the solution decreases regularly and smoothly with increasing temperature until to the specific coil-globule transition temperature of P NIPAM (around 32 degreesC) and afterwards it increases with increasing temp erature on the contrary. This extraordinary phenomenon is successfully expl ained and treated by a quantitative theory in terms of accompanying solvati on-desolvation process in the course of coil-globule transition of the poly mer chain in solution.