抄録
The thermal properties of N-isopropylacrylamide (NIPA) gels in water have been investigated with differential scanning calorimetry (DSC). The dissociation enthalpy of hydrophobic bonding per NIPA monomer, ΔHN and the number of water molecules associated with the dissociation, (n-n0), were evaluated as a function of the gel preparation temperature, Tprep, where n and n0 are the number of water molecules per NIPA mole before and after dissociation, respectively. It was found that ΔHN is independent of Tprep. On the other hand, both n and n0 increase with increasing Tprep, while the difference, i.e., (n-n0) is constant irrespective of Tprep. These experimental findings suggest that the enthalpy and the number of water molecules associated with the dissociation are independent of Tprep although the number of trapped water molecules increases with Tprep in both the swollen and shrunken states.
