Fast-responding bulk hydrogels with microstructure

A new method was used for the production of fast-responding bulk hydrogels with microstructure (BHMs) with a high swelling ratio. These BHMs were synt hesized first by the formation of poly(N-isopropylacrylamide-co-acrylic aci d) (NIPAAm-AA) microgel particles and then by the crosslinking of the parti cles with N-isopropylacrylamide monomer. The polymer obtained had the desir ed microstructure but was bulk (monolithic), so it could be used in a varie ty of applications. The NIPAAm-AA microgel particles were characterized wit h transmission electron microscopy, and the formed BHMs were characterized with scanning electron microscopy. Compared with conventional bulk hydrogel s, the BHMs had very high swelling ratios and much faster swelling rates at tributable to the collaboration of the ionized microgel particles and bulk hydrogels. An increase in the microgel particles embedded in the BHMs provi ded faster hydrogel swelling. The number of ionic acrylic acid groups in th e hydrogels affected their swelling behavior. (C) 2002 John Wiley & Sons, I nc.