Viscoelastic scaling of colloidal gels in polymer solutions

The structure and formation of particulate silica networks in biopolymer solutions were studied using rheological measurements and diffusing wave spectroscopy (DWS). For samples with different volume fractions of silica, the frequency-dependent viscoelastic moduli can be scaled onto one master curve by shifting the data along the moduli and frequency axes. Viscoelastic scaling of silica suspended in carboxy methyl cellulose (CMC) solution shows a linear relationship between the scaling factors. For silica suspensions in xanthan solutions, only vertical scaling is needed to obtain the master curve. It was found that the elasticity of the polymer matrix affects the structure of particulate networks as well as the kinetics of structural recovery after preshear. The fractal dimension of the silica network was found to be lower in polymer solutions with high elasticity (xanthan) in comparison to those with low elasticity (CMC). DWS measurements reveal strongly subdiffusive and nearly diffusive motion of particles in xanthan and CMC solutions, respectively. The difference in mobility of particles explains structural differences between silica networks formed in CMC and xanthan solutions as well as different kinetics of viscoelastic recovery after shear.