Structural changes in polymer gels probed by fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy (FCS) was used to provide quantitative measurements on the diffusion of particles in polymer systems. The FCS was applied to measure the diffusion time of fluorescent (TAMRA) molecules in poly(vinyl alcohol) (PVA) solutions and gels prepared at various polymer concentrations and cross-link densities. The measurements indicate that the diffusion of probe particles is affected not only by the polymer concentration but also by the cross-link density of the gel. A simple linear relation between the diffusion times and the elastic moduli of the same gels was also found.