Over the last decade, the concept of utilizing nanoparticles to enhance polymer performance has drawn a great deal of research interest. Significant property enhancement can be achieved with addition of a small amount of nanoparticles. Spherical, platelet or tube/fiber like particles have all been used in the fabrication of nanocomposites. Our major interest lies in platelet clay nanoparticles and multiwall carbon nanotube (carbon nanofiber or CNF).

We studied free radical polymerization of methylmethacrylate (MMA) and styrene (St) in the presence of clay nanoparticles. A reactive surfactant was synthesized to modify the clay surface. By careful choice of reaction conditions, exfoliated nanocomposites were synthesized using both matrices. Shown in Figure 1 is a comparison of clay dispersion in PS as a result of different clay surface treatment. Two-dimensional nano-sized particles, carbon nanofiber (CNF) was also applied to synthesize polymer nanocomposites.

In addition to thermoplastic nanocomposites, we are investigating the consequences of added layered-silicate (size, chemical functionalization and concentration) on the reaction and rheological behaviors, as well as the structure and properties of the resulting thermoset nanocomposite. The aim of this work is to provide a comprehensive set of structure - property relations for layered-silicate based nanocomposites. In particular, our research results showed that a small amount of nanoclay could provide excellent volume shrinkage control of low profile unsaturated polyester resin systems cured at room temperature ( Table 1), resulting from preferential partitioning of clay into low profile additive (LPA) rich phase ( Figure 2). It will show great efficiency to overcome a number of molding problems caused by their high polymerization shrinkage (approximately 7-10%) of unsaturated polyester resin, such as poor surface quality, dimension instability of the molded parts, and internal stress and microvoid ( Figure 3). We are investigating the nanoclay partition during the reaction-induced phase separation due to the nanoclay surface functionality. Research in this area is directed at elucidating how the nanoclay partition affects the two phases curing behavior and its influence on the volume shrinkage and surface quality of the resulting composites.