Dynamic-light-scattering experiments on semidilute aqueous solutions of gelatin indicate three relaxation processes: an exponential for times less than ∼50 μsec followed by a power law at intermediate time and then a stretched exponential at long time. The characteristic time of the stretched exponential diverges as the system evolves to a gel. The latter two relaxations can be explained in terms of an anomalous diffusion mechanism where the mean-square displacement behaves as 〈${\mathit{R}}^2$〉∼lnt at intermediate time and 〈${\mathit{R}}^2$〉∼${\mathit{t}}^{\mathrm{\beta }}$ with β<1 at late time. Length scales derivable from these diffusion mechanisms obey scaling, and it is proposed that β is related to the fracton density-of-states exponent and the fractal dimension of the gelatin molecules.

• Received 25 September 1991

DOI:https://doi.org/10.1103/PhysRevA.45.2416