Fluorescence anisotropy of dyes included in crosslinked polystyrene

In this work we investigate on the local free volume of a crosslinked polys tyrene by studying the steady-state fluorescence anisotropy of three probes with different sizes and shape, embedded in the polymer matrix. The very l ow values measured for the steady-state fluorescence anisotropy show that t he molecules can perform ample movements during their excited-state lifetim es (typically few nanoseconds). Moreover, anisotropy values decrease with t he size of the probe. Results were interpreted in terms of Saupe order para meters and the wobbling-in-cone model. (C) 1999 Elsevier Science S.A. All r ights reserved.