Photon transmission technique for monitoring swelling of acrylamide gels formed with various crosslinker contents

Photon transmission experiments were performed using a UV-visible (UVV) spe ctrometer during the swelling of polyacrylamide (PAAm) gets. These gels wer e prepared from acrylamide (AAm) with various N,N ' -methylenebisacrylamide (Bis) contents by free-radical crosslinking copolymerization (FCC) in wate r and dried before use for swelling experiments. Transmitted light intensit y, I-tr increased at very early times when PAAm gels are immersed in water, then decreased continuously as swelling time is increased. Decrease in I-t r was attributed to the increase in the scattered light intensity, I-sc whi ch may originate from the contrast between 'frozen blob clusters' and holes in the swelling gel. Decrease in I-tr was modelled using the Li-Tanaka equ ation from which time constants, tau (1), and collective diffusion coeffici ents, D-0 were determined for various Bis content PAAm gels. tau (1) and D- 0 were found to be strongly correlated with the wavelength, lambda of I-tr and the Bis content of the gel samples. The correlation between lambda and tau (1) and D-0 predicts the existence of 'frozen blob clusters' in PAAm ge ls. (C) 2001 Elsevier Science Ltd. All rights reserved.