(532a) Interfacial Behavior of Modified Silicone Polymers and Their Interactions with Solid Substrates

Unique nanostructures with special properties are exhibited by silicones which are simultaneously hydrophobic and oleophobic. While silicones are utilized in a number of applications, the fundamental reasons behind their special behavior are unknown. This work focuses on understanding the modifications of micro and macro surface properties of materials as a function of the modifications of silicone polymers. It was observed using AFM that the silicone treated fibrils are uniform, well stacked and smoother than the untreated fibers. On a macroscopic scale 20% reduction in frictional coefficient of the fabric was observed after treatment with quaternized silicones. It is hypothesized that the size distribution and charge of silicone emulsions decide the nature of the modification of the substrate properties. With bimodal droplet distribution of silicone emulsions, the nano-sized droplets penetrate deeper into the substrate to provide bounciness, whereas macro-sized droplets can coat the top layer leading to friction reduction. Spectroscopic analysis of treated fibers using RAMAN and ATR indicated a decrease in fiber stress as a function of modification of silicone polymer and the interaction pH. It was observed that at high pH the zetapotential of silicone emulsions decreases drastically and the nano emulsions turn turbid. It is postulated that the observed electrophoretic and nephelometric behavior at high pH is due to flocculation of nanosized droplets to micron size, which eventually leads to emulsion destabilization. It is also postulated that the nano emulsion undergoes a critical dilution concentration (CDC), which lead to rapid coalescence. Therefore the surface properties of the substrate obtained above the CDC are significantly different than those below the CDC. The research is intended to develop structure-property-performance relationship of modified silicone polymers and films at various interfaces (air/liquid, liquid/liquid and solid/liquid).