VISCOSITY BEHAVIOR OF POLYELECTROLYTE COPOLYMERS CONTAINING SULFONATEGROUPS IN MIXED ORGANIC-SOLVENTS

Copolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS, monomer I)with 2-hydropropyl methacrylate (HPM, monomer 2) was conduct ed in ethylene glycol/water (1 : 1 in weight) at 70 degrees C. The rea ctivity ratios estimated from the copolymer composition at low convers ion are r(1) = 2.31 +/- 0.25 and r(2) = 11.70 +/- 1.05. The azeotropic composition was found at the monomer mole ratio AMPS/HPM equal to 8/2 . Viscosity of these copolymers was measured in dimethyl sulfoxide (DM SO) and DMSO/tetrahydrofuran (THF) mixed solvent at 25 +/- 0.05 degree s C. Polyeletrolyte behavior was observed for all the copolymers, even in the mixed solvent containing 65 wt % of THF. The reduced viscosity at constant polymer concentration decreased with increasing THF conte nt in the mixed solvent. The copolymers having AMPS repeat units more than 42 mol % precipitated in the mixed solvent when the THF was beyon d 68 wt %. The viscosity reduction and precipitation in the copolymer solutions with increasing THF can be attributed to the dipole-dipole a ttraction between ion-pairs formed in less-polar medium. This is helpf ul in understanding the volume phase transition in highly charged hydr ogels caused by mixing solvents. (C) 1997 John Wiley & Sons, Inc.