Drying of heterogeneous hydrogels formed with various water contents: A photon transmission study

Drying of acrylamide (AAm) gels was monitored by using a photon transmissio n technique. These hydrogels are formed from AAm and N,N'-methylenebis(acry lamide) (Bis) with various water contents by the free-radical crosslinking copolymerization (FCC). The transmitted light intensity, I-tr, increased co ntinuously as AAm gels were dried. The increase in I-tr was attributed to t he decrease in the scattered light intensity, I-sc, which might be originat ed from the contrast between frozen blob clusters and holes in the drying g el. A decrease in I-sc was modeled by using Rayleigh's equation where dryin g times with various exponents were found to be proportional to the size of the holes. It was observed that the radius of holes, xi (c), decreased in various powers of the drying time depending on water content used during FC C. (C) 2001 John Wiley & Sons, Inc.