Dynamics and microstructure of charged soft nano-colloidal particles

The microstructure and rheological properties of swellable nano-particles consisting of cross-link methacrylic acid/ethyl acrylate were examined using dynamic light scattering (DLS) and rheological techniques. A unified semi-empirical approach for predicting the viscosity of dilute and concentrated systems was proposed, where a variable specific volume, k was introduced to convert the mass concentration to effective volume fraction. The viscosity data for four different microgel systems showed excellent agreement with the modified Krieger–Dougherty model. The parameters, c0 and m for the expression, k−kmin/k0−kmin=[1+(c/c0)2]−m as a function of degree of neutralization (α) were determined. We observed that c0 decreases with α, while m increases with α. The validity of the new approach was compared against the theoretical model for determining the effective volume fraction, φ=(Q̃/Vmc0)(ρs/ρp)c and excellent agreement was observed.