Dynamics of cellulose whiskers in agarose gels. 1. Polarized dynamic light scattering

The dynamics of cotton cellulose microcrystals ("whiskers") trapped in agarose hydrogels of varying concentrations was studied by polarized dynamic light scattering. The rigid agarose network strongly heterodynes the signal of the mobile whiskers, thereby enabling the measurement of their diffusion coefficient D and their fluctuating scattered intensity R-theta. For low agarose gel concentrations, i.e., when the mesh size of the agarose network is larger than the length of the whiskers, the dynamics does not depend on the whisker content. The product of D and R-theta, which is inversely proportional to the friction coefficient, is independent of the gel concentration, indicating that the network does not hinder the whiskers. When the mesh size of the network is smaller than the length of the whiskers, the whisker content influences the dynamics and the product RthetaD becomes dependent on the gel concentration; i.e., frictional effects arise. Also in this condition domains with different whisker contents may develop in the gel.