Anomaly in rotational diffusion of photophysical probe near volume phase transition of copoly(acrylamide-acrylic acid) gels: Steady state and time-resolved fluorescence study

Changes in the microenvironment of pyrene-labeled copoly(acrylamide-acrylic acid) gels are investigated by means of fluorescence spectroscopy. An anom aly in the microscopic motion of a pyrenyl probe was observed in the vicini ty of the phase transition: the average lifetime of monomer emission approa ched zero, and the rotational diffusion constant of pyrenyl probe became in finite. Density fluctuation and the nonequilibrium situation near the phase transition are considered to cause the rapid microscopic fluctuation of th e network and solvent molecule.