Fast transient fluorescence (FTRF) technique to study swelling of densely and loosely formed gels

A Strobe Master System (SMS) is introduced for studying the swelling of cyl indrical densely (DG) and loosely (LG) formed gels. Gels were prepared by f ree radical copolymerization of methyl (methacrylate) (MMA) and ethylene gl ycol dimethacrylate (EGDM). Pyrene (P) was introduced as a fluorescence pro be during polymerization, and the lifetimes of P were measured using (SMS) during in situ swelling processes. Chloroform was used as a swelling agent. A model is derived for low quenching efficiencies to measure mean Lifetime s [tau] of P, and it was observed that [tau] values decreased as the swelli ng proceeded. The Li-Tanaka equation was employed to determined the time co nstants, tau(c), and cooperative diffusion coefficients, D-c, which were fo und to be around 400 min and 10(-5) cm(2)s(-1), respectively. No difference s were detected in tau(c) and D-c values of DG and LG gels. Quenching rate constants, kappa, and the; mutual diffusion coefficient, D-m, were measured and found to be around 10(5) M(-1)s(-1) for DG and LG gel samples. (C) 200 0 John Wiley & Sons, Inc.