1. Pressure dependence on the Flory-Huggins interaction parameter of poly(N-isopropylacrylamide) gels
- Author
-
Tadayoshi Kitada, Eiji Kato, and Chikanobu Nakamoto
- Subjects
Quantitative Biology::Biomolecules ,Polymers and Plastics ,Chemistry ,General Chemical Engineering ,Enthalpy ,Hydrostatic pressure ,Pharmaceutical Science ,Thermodynamics ,Flory–Huggins solution theory ,law.invention ,Gibbs free energy ,Condensed Matter::Soft Condensed Matter ,Hydrophobic effect ,chemistry.chemical_compound ,symbols.namesake ,law ,Volume fraction ,Poly(N-isopropylacrylamide) ,symbols ,Hydrostatic equilibrium - Abstract
Pressure dependence of the Flory-Huggins interaction parameter for poly (N-isopropylacrylamide)/water gel is obtained by measuring the swelling ratio of the gel in equilibrium under hydrostatic pressure up to about 100 MPa and by employing a mean field theory based on the Flory-type of the Gibbs free energy formula. The interaction parameter strongly depends on the volume fraction of a gel network and also on solvent pressure. In the swollen phase equilibrium of a gel under pressure, both the enthalpy and entropy increase with pressure, the second virial term decreases inversely and the interaction parameter is an increasing function of pressure. It can be seen that hydrostatic compression strengthens the hydrophobic interaction between polymer segments because of a loosening hydrogen-bond structure near the monomer unit.
- Published
- 1996
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