(119a) Design, Control and Direct Visualization of Heterogeneous Structure in Colloidal Aggregates and Gels (Invited Talk)

Gels and aggregates composed of colloidal particles interacting through short-range attractive forces are common in the production of ceramics, membranes, optical fibers and other materials. Aggregation and gelation also compete and interfere with the assembly of ordered colloidal structures. Here we study the relationship between heterogeneous structure in colloidal aggregates and gels and the potential interactions between the colloids. Gelation is induced in density-matched suspensions of fluorescent colloidal poly(methyl methacrylate) by the addition of non-absorbing polymer. A three-dimensional volume of the gels is visualized by confocal microscopy. The pair correlation function, contact number distribution and length-scale dependence of number-density fluctuations are quantified as a function of the amount of non-absorbing polymer added. We correlate the strength of two-body potential interactions with the degree of structural heterogeneity and particle localization in the aggregates and gels.