Volume Phase Transition of Polymer Gels

Abstract

Experimental and theoretical studies performed on thermoshrinking N-alkylacrylamide gels are described. Equilibrium swelling ratios are presented for the gels in the presence of no additives, a surfactant (SDS), inorganic salts, polar organic components and tetraalkylammonium bromides. The gel studies are carefully matched to polymer cloud point studies and it is shown that the hydrophobicity of the monomer unit of the polymer greatly controls the phase behavior. A new model which can describe not only thermoswelling but also thermoshrinking types of volume phase transitions is presented. Dynamical studies performed with light scattering during spinodal decomposition provide new information on diffusion coefficients and mass transfer in the gels. Our studies provide new data on the use of a gel in membrane applications. We report permeation characteristics of a composite membrane of thermosensitive gel and porous glass. These include volume flux and rejection properties. It is pointed out that the change in the permeation characteristics results from that in micropore structures of the gel.