Spinodal dynamics in cluster aggregation

Abstract
We report small angle static light scattering measurements on colloidal aggregation at high monomer volume fractions. The structure factor S(q) exhibits a pronounced maximum at a finite wave vector q_m at any stage during the aggregation reaction. In the later stages the structure factor scales accordng to a universal law similar to that of spinodal decomposition dynamics : [MATH]. At variance with spinodal decomposition, where d = 3, we find d = d_f, the fractal dimension of colloidal clusters. The aggregation stops when the peak position reaches a certain value q* which depends on the monomer concentration. The terminal stage occurs when all the sample is filled with close packing fractal clusters of size R α 1/q*