Abstract: Radical copolymerization of 2-acrylamido 2-methylpropane sulfonic acid(AMPS) with 2-hydropropyl methacrylate(HPM) was conducted in ethylene glycol/water(1∶1 in weight) at 70 ℃. The azeotropic composition was found at the monomer molar ratio of AMPS/HPMas 8/2. Three sulfonic gels were prepared at this composition with the crosslinker N,N'-methylene-bis(acrylamide) of 2%, 3% and 5%(molar percentage), and referred to as G02, G03 and G05, respectively. As expected from their polyelectrolyte nature, these gels swell in dimethyl sulfoxide(DMSO) but shrink in tetrahydrofuran(THF) at 25 ℃. The volume phase transition takes place in the G02 and G03 swollen in DMSO/THF mixtures when THFcontent is increased beyond 55%～60%(volume ratio). In ethanol/THF mixture, however, no volume phase transition was found though the gel still shrunk with increasing THF. The dipole dipole interaction model in less-polar medium was adopted to interpret these results with the concept of preferential solvation.

Key words: Sulfonic acid gel, Swelling, Volume phase transition, Dipole-dipole interaction, Polyelectrolyte