Thermodynamics of swelling of poly (N-isopropylacrylamide-co-N-tertiarybutylacrylamide-co-acrylamide) hydrogels

In the present study, the swelling properties of poly (NIPAM-co-NTBA-co-AAm) hydrogels have been discussed. The enthalpy change of mixing ?Hmix, entropy change of mixing ?Smix, free energy change of mixing ?Gmix were determined for swelling of hydrogels at 25oC. ?Hmix and ?Smix were found to be decreased with increasing the crosslinking ratio. The value of ?Gmix and ?Gela are found to be increased with increasing the crosslinking ratio followed by decrease in swelling percentage. The Overall results indicate that negative free energy supports more swelling percentage. At all temperatures the equilibrium swelling percentage of the hydrogels are found to be increased with decreasing the crosslinking ratio.