Two-stage swelling of acrylamide gels: A photon transmission study

Acrylamide gels were prepared from acrylamide (AAm) with various N,N'-methy lenebis(acrylamide) (Bis) contents by free-radical crosslinking copolymeriz ation (FCC) in water and dried before used for swelling experiments. Photon transmission measurements were performed using a UV-visible (UVV) spectrom eter during the swelling of polyacrylamide gels. Transmitted light intensit y I-tr increased linearly at very early times when acrylamide gels were imm ersed in water, then decreased continuously as swelling time increased. The behavior of I-tr was modeled assuming two-stage swelling mechanisms for th e swelling acrylamide gels. The increase in I-tr at early times was quantif ied using a linear diffusion model and a linear relaxation constant ko was measured. The decrease in I-tr was modeled using the Li-Tanaka equation, fr om which time constants tau (1) and cooperative diffusion coefficients D-0 were determined for acrylamide gels with varying Bis content. (C) 2001 John Wiley & Sons, Inc.