(640c) Polymer Silica Composite Nanofibers Via Sol Gel Electrospinning

In recent years, polymer-silica composites with enhanced thermal and mechanical properties have found applications in a variety of fields including catalysis, adsorption, pervaporation, sensors, and enzyme encapsulation. Scope of application of these composites can be further broadened by transforming them to nanofibrous structures with high surface to volume ratios. In this work, we have employed a controlled sol−gel synthesis incorporated with electrospinning to produce polymer silica composite nanofibers. We used polyvinyl alcohol (PVA) and polyacrylonitrile (PAN) as the polymer phase and by mixing PAN or PVA with silica precursor, we produced electrospun composite fibers having varying properties depending on the polymer phase and nature of the sol gel processed silica. We systematically investigated the effects of i) silica precursor mixture composition, ii) silica-polymer ratio, and iii) aging time of the silica precursor mixture, on the fiber properties.

Stabilized carbonization of PAN silica composite fibers at 800 °C transformed the fibers to carbon silica composite nanofibers with smooth morphology and diameter ranging from 400 to 700 nm. FTIR analysis of the fibers confirmed the presence of silica in the as-spun as well as the carbonized material. Role of silica in modifying the graphitic character of the carbon-silica fibers is studied through Raman analysis. When soaked overnight in water, the PVA silica composite nanofibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. FTIR analysis of the fibers further helps us to propose that mixing silica precursor with PVA in solution initiates the participation of the silica precursor in cross-linking of PVA, so that its −OH group becomes unavailable for hydrogen bonding with water. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica broadens the scope of these materials in various technologies.