(213e) Experimental and Theoretical Investigation of Organically Modified Clay Dispersed in Organic Solvent for Production of Polymer-Clay Nanocomposites

Polymer nanocomposite materials exhibit enhanced properties relative to ordinary polymers. Here, we describe recent work concerning the development of novel polymer-clay nanocomposites. One route for the production of these materials is to disperse clay in a polymerisable monomer solvent. When a desired degree of clay dispersion is achieved the solvent can be polymerised in-situ to obtain the nano-composite material. Our work attempts to control the morphology of the clay particles in the liquid precursor solvent, with the aim of producing a range of polymer-clay nanocomposite materials with a range of properties depending on the type of polymer, type of clay, and morphology of dispersion. Although previous work indicated that full exfoliation, and possibly full dispersion, of organically modified clay in monomer solvent can be achieved under appropriate conditions, and hence that the phase behaviour of dispersed clay can be controlled, we find that this is not the case. Instead, we find using static light scattering that under such conditions organically modified clay particles in organic monomer solvents tend to aggregate to form clusters and possibly weakly-bound percolating networks even at very low clay loadings. We find that these clusters and networks are present even in clear, non-sedimenting, apparently fully dispersed systems, where small angle X-ray scattering shows no visible signatures of stacking or other short-range platelet order. By comparing experimental scattering results with meso-scale simulations we can gain some insight into the structures obtained, and hence gain some understanding of how our ultimate aim of full dispersal could be achieved. Moreover, the simulations reveal a wealth of self-aggregation behaviour driven by subtle changes in effective clay-clay interactions. This information might be useful in designing new materials using discotic nanoparticles.