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 acid). The resultant chemically 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 (Tc). Additionally, the replacement of BIS by GLY yielded a decrease in the Tc 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.