Diffusion analysis of gelatin solutions by photocorrelation spectroscopy

The diffusion coefficients and polydispersities of polydisperse gelatin solutions are studied by photocorrelation spectroscopy. The method of cumulant analysis is used in analyzing the autocorrelation data. The z-average diffusion coefficients and polydispersities of the gelatin solutions are obtained from the first and second order cumulants, respectively. Gelatin particles are freely dispersed at low concentrations, but form polymer networks at high concentrations. The z-average free diffusion coefficient is independent of concentration and is proportional to q². The hydrodynamic radii and polydispersities of the gelatin molecules at different salt concentrations and temperatures are also studied. The results lead to the conclusion that most of the aggregates are covalently linked and that hydrogen-bonded and collagen-folded aggregates do not make significant contributions to the overall aggregate makeup even at temperatures as low as 20°C.