Synthesis of polymer nanocomposites via in-situ emulsion polymerization from functionalized nanomaterials

Abstract

Dual step process for nanomaterials functionalization was developed; the first step improved the dispersibility of the nanomaterial to assist improving efficiency of the second step, reaction with oleic acid in mild condition. The functionalization was efficient for CNT (carbon nanotubes) and silica, which assisted to utilize in-situ emulsion polymerization, not commonly reported though a versatile technique, to synthesize PS/CNT and PS/silica composites. Investigation revealed improvement of nanocomposites properties and potential for practical application. For the investigated properties, oleic acid functionalization showed superiority. The pH effect on raw CNT dispersion was found to improve the CNT dispersion, which was utilized to substitute the first step of the developed dual step approach of CNT functionalization. Organic acids, i.e., methacrylic acid and acrylic acid were investigated as functionalizing agents for CNT functionalization, and found effective via relevant investigation. Chain transfer agent (CTA) was introduced in nanocomposite syntheses with oleic acid functionalized CNT to investigate its effect, which reduced the molar mass. The major difference between the nanocomposites with or without CTA was the absence of free CNT for nanocomposites with CTA. This influenced the nanocomposites properties substantially. The electrical properties of PS/CNT nanocomposites with or without CTA were tested via electrochemical impedance spectroscopy (EIS), which were found altered at wide frequency range. The measurements and modeled electrical equivalent circuits (EEC) explained the structural orientation of the CNT in nanocomposites, which was in agreement with the microscopic images. Finally, polymer brush nanocomposites were synthesized via in-situ emulsion polymerization, not commonly reported for such synthesis. Oleic acid functionalized CNT were further modified via organo silane chemistry. The developed synthesis scheme was confirmed via identification of the functional groups and polymer attachment on CNT surface. Synthesized polymer brush nanocomposites displayed enhanced thermal and gas adsorption property.