RUI: Fractal Structure Formation from Poly(vinyl alcohol) Adsorption on Silicone Substrates

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NON-TECHNICAL SUMMARY:Poly(vinyl alcohol) (PVOH), a nontoxic and water-soluble polymer, spontaneously attaches itself to silicone substrates from water solution and forms "fractal" (tree-branch like) structures from nanoscopic to macroscopic scales. The objectives of the proposed work are to explore the formation mechanism of PVOH fractals on silicone substrates and to probe the material and experimental factors controlling the structural features of PVOH fractals. The polymer fractal formation dynamics will be imaged during their actual generation using optical microscopy; the fractal structures from the nanometer to micrometer scales will be characterized by various microscopy techniques. Wettability and other surface characteristics of the silicone substrates, before and after PVOH adsorption, will also be analyzed to assess the effect of the fractal polymers on substrate properties. The funds requested will support the proposed scientific research involving a number of undergraduate students at Mount Holyoke College and local female high school students over the next three years. With the proper training, mentoring, and encouragement, the students will gain competency and confidence in scientific research and will be better prepared for the next phase of their educational endeavors.TECHNICAL SUMMARY:Poly(vinyl alcohol) (PVOH) spontaneously adsorbs from aqueous solution to silicone substrates and forms unusual fractal structures at multiple length scales. The crystalline nature of PVOH and the unique properties of silicone thin films (molecular flexibility, low surface tension but high water compatibility) will be probed in exploring the conditions for fractal formation. The dependence of fractal features (size, density, and dimensionality) on experimental variants (silicone thickness and composition, PVOH molecular weight and degree of hydrolysis, and adsorption parameters) will also be the focus of the proposed work. Atomic force and optical microscopy will be used to image dynamically PVOH fractal formation on various silicone substrates in-situ and to analyze the fractal features from nanoscopic to macroscopic scales. Contact angle goniometry and ellipsometry, in addition to various other surface techniques, will be utilized to characterize the silicone substrates, before and after PVOH adsorption, to assess the effect of the fractal adsorbed polymers on substrate surface chemistry and properties. The proposed research will not only establish a new system to prepare fractally branched polymers with controlled structural features, but will also provide insights on material and experimental requirements for fractal polymer formation. The funds requested will support research involving a number of undergraduate students at Mount Holyoke College and local female high school students over the next three years.