New superabsorbent thermoreversible hydrogels

The novel octafunctional crosslinker glyoxal bis(diallylacetal) (GLY) was employed in the synthesis of thermosensitive hydrogels of (N-isopropylacrylamide -co-acrylic ac id). The resultant che mic ally crosslinked networks show levels of swellability in water significantly higher than those previously reported for such copolymers crosslinked by N,N'-methylene bisacrylamide (BIS) whilst retaining the ability to deswell at temperatures above the lower critical temperature (T-c). Additionally, the replacement of BIS by GLY yielded a decrease in the T-c of the hydrogels, indicating that incorporation of GLY into the polymer network increases the hydrophobicity of the network; this is consistent with the structure of GLY and its sparing solubility in water. (C) 2000 Elsevier Science Ltd. All rights reserved.