VOLUME PHASE-TRANSITION OF POLYELECTROLYTE GELS IN DIMETHYL SULFOXIDETETRAHYDROFURAN MIXTURES/

Copolymer gels were prepared from 2-(acrylamido)-2-methylpropanesulfon ic acid (AMPS), N,N-dimethylacrylamide (DMAA, comonomer) and N,N'-meth ylenebis(acrylamide) (BIS). The mole fraction of AMPS were 0.2674 and 0.4318, respectively, with the same BIS mole fraction of 0.013. These gels with counterions H+, Na+, and K+ were swollen at 25 degrees C in mixtures of dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF). A vol ume phase transition was observed at the THF volume fraction of about 0.58, indicating that the volume phase transition in a polyelectrolyte gel occurs when the medium polarity decreases sufficiently for ion-pa ir formation. On changing the counterion, the fraction of DMSO in the solvent mixture which is required to initiate swelling decreases in th e order Na+, H+, and K+, the same as for counterion condensation in id entical gels. Copyright (C) 1996 Elsevier Science Ltd.