Adhesive hard-sphere colloidal dispersions: Fractal structures and fractal growth in silica dispersions

Abstract

Silica particles coated with octadecyl chains and dispersed in linear alkanes (dodecane and higher alkanes) show gelation upon cooling. The structure of these gels can be characterized in terms of a fractal dimension ${d}_{f}$=2.1. Aggregation and gelation at temperatures just below the cloud point (the temperature at which phase transition occurs) have been studied by light scattering and are described in terms of the finite linear cluster size (cluster radius) \ensuremath{\xi} of the growing fractal. This size is found to increase linearly with time. The influence on ${d}_{f}$ of quench temperature, volume fraction, particle size, and solvent type is discussed.