FLUORESCENCE DEPOLARIZATION AND QUENCHING STUDIES OF ACENAPHTHALENE-LABELED POLY(ACRYLAMIDE) IN WATER

Acenaphthalene was copolymerized with acrylamide in water to form poly(acrylamide-co-acenaphthalene) [P(AAm-co-ACE)] with molecular weight almost-equal-to 2 x 10(6) g mol-1. A variety of fluorescence experiments were carried out at 0.8 wt% polymer concentration. Time-resolved fluorescence depolarization measurements gave a mean rotational correlation time for backbone motion of 30 ns. Time-resolved and steady-state fluorescence quenching experiments were carried out using acrylamide as the quencher. In the case of polymer-bound chromophore, we were able to follow the transient effect in the diffusion-controlled quenching process. The mutual diffusion coefficient D characterizing this reaction is a factor of six slower than the self-diffusion coefficient D(AAm) = 9.15 x 10(-6) cm2 s-1 for acrylamide in water, measured by pulsed gradient n.m.r. We interpret this result to mean that acrylamide diffusion is significantly slower inside the P(AAm) coil than it is in bulk water.