Self-assembled nanoparticle capsules and their aggregation in anisotropic liquid crystal solvent

The mutual attraction between colloidal particles in an anisotropic fluid, such as the nematic liquid crystal phase can lead to the formation of hierarchical aggregate morphologies distinct from those that tend to form in isotropic fluids. Previously it was prohibitive to study this aggregation process for a large number of colloids due to the difficulty of achieving a well dispersed initial colloid distribution. I will be talking about a self-assembling colloidal system, recently developed by our group, to investigate this process. Hollow, micron-scale colloidal capsules are formed in-situ in the nematic phase and subsequently aggregate to produce fractal structures and dense gels, the structure of which is determined by capsule concentration and temperature quench depth through the isotropic to nematic phase transition point. This self-assembling colloidal system provides a unique method to study particle aggregation in liquid crystal over large length scales. We use confocal fluorescence microscopy over a wide range of length scales to measure aggregate structure as a function of temperature quench depth, observe ageing and explore the driving mechanisms in this unique system. Our analysis reveals that aggregate dynamics depend on a combination of Frank elasticity relaxation, spontaneous defect line annihilation and internal fracturing.