Investigation of colloidal properties of modified silicone polymers emulsified by non-ionic surfactants

Functionalized silicones are a unique class of hybrid materials due to their simultaneous hydrophobic-oleophobic properties, which results in applications in a variety of surface modification techniques. Prior research has shown that changes in surface charge and turbidity of modified silicone emulsions as a function of pH have a marked effect on their performance in coating applications. The emulsion droplet size is also believed to play significant role in such coating applications. In this work, modified silicone polymer emulsions stabilized by non-ionic surfactants were studied using dynamic light scattering (dilute) and electroacoustic (concentrated) spectroscopy to monitor the emulsion droplet size. The dilute and concentrated regime studies showed the emulsion droplet to be in nanometer range with no appreciable change in size as a function of pH. Electroacoustic studies showed a small fraction of droplets to be present in the micron size range. The emulsions were examined using Cryo-TEM technique, and the effect of pH and dilution on hydrophobicity of nanodomains was studied by employing fluorescence spectroscopy. It is shown from pyrene excimer behavior that both the dilution and pH have an effect on emulsion stability with a presence of critical surfactant concentration after which the emulsion was destabilized. It is proposed that the emulsion stability characteristics and the particle size distribution both play a significant role in their ability to impart desired macro and nano surface properties to treated substrates through electrostatic interactions and selective binding.