Properties of smart hydrogels composed of polyacrylic acid/poly(vinyl sulfonic acid) responsive to external stimuli

Smart hydrogels, random copolymers composed of poly(acrylic acid) and poly(vinyl sulfonic acid), were prepared. The swelling ratios at various temperatures and pHs, the deswelling water ratio under an electric field, and the free water and bound water contents of the hydrogels were measured. The hydrogels exhibited very high swelling ratios, in the range of 8200%-18000%, at 37 degreesC, and showed temperature- and pH-dependent swelling behaviour. The deswelling water ratio of the hydrogel sample CO1 showed a weight reduction of about 80% under a 5 V applied voltage. The free water contents in hydrogel samples CO1, CO2 and CO3 were 47.71%, 40.92% and 37.27% respectively in pure water.