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The temperature dependence of the specific refractive index increment d n /d c of aqueous poly( N isopropylacrylamide) solution in the range of 20 ℃ to 35 ℃ were determined by a differential refractometer. The measured d n /d c of the solution decreases regularly and smoothly with increasing temperature until to the specific coil globule transition temperature of PNIPAM (around 32 ℃) and afterwards it increases with increasing temperature on the contrary. This extraordinary phenomenon is successfully explained and treated by a quantitative theory in terms of accompanying solvation desolvation process in the course of coil globule transition of the polymer chain in solution.
The temperature dependence of the specific refractive index increment dn / dc of aqueous poly (N isopropylacrylamide) solution in the range of 20 ° C to 35 ° C was determined by a differential refractometer. The measured dn / dc of the solution decreases regularly and smoothly with increasing temperature until to specific coil globule transition temperature of PNIPAM (around 32 ° C) and afterwards it increases with increasing temperature on the contrary. This extraordinary phenomenon is successfully explained and treated by a quantitative theory in terms of accompanying solvation desolvation process in the course of coil globule transition of the polymer chain in solution.