RUI: Poly (vinyl alcohol) Thin Film Dewetting by Controlled Directional Drying

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Part 1: NON-TECHNICAL SUMMARYPolymer thin films are ubiquitous in everyday life. Typically, thin-film stability is desirable, such as in the application of coating materials. However, controlled dewetting or thin-film rupture can also be beneficial, for example in printing and other lithographic processes. Most of the existing studies have involved nonvolatile and nonpolar thin films. The stability of polymer thin films prepared from a volatile and polar liquid, such as water, has practical and fundamental significance and should be investigated. This research involves the fabrication of thin films of poly(vinyl alcohol) (PVOH), a water-soluble and non-toxic polymer, on silicone-coated silicon substrates using a new method called adsorptive spin casting. This method allows the spontaneous adherence of PVOH polymer to the silicone surfaces from water as well as the controlled rupture of PVOH thin films due to directional water evaporation. The study will systematically investigate under- or unexplored areas in polymer thin film stability, such as the (de)stabilization effect of a polar solvent, unconventional thin-film rupture patterns, and the effects of substrate mobility and polarity. As an educator and a female scientist in the longest-standing liberal arts college for women, the PI is committed to improving the representation and retention of women in the STEM disciplines. She will recruit and mentor a diverse group of undergraduate women to carry out new, relevant, publishable, and productive research proposed herein. With the proper structure, challenge and support, the students will gain competency and confidence for their future endeavors in the STEM fields.Part 2: TECHNICAL SUMMARYStability and controlled dewetting of polymer thin films have practical, technological, and fundamental significance. Studies of polymer thin films prepared from aqueous solution have been limited due to the particular challenges involved in elucidating the effects of drying dynamics and solvent polarity on thin-film stability. In the proposed research, poly(vinyl alcohol) (PVOH) thin-film dewetting on silicon wafer-supported polydimethylsiloxane (PDMS) will be studied using a new fabrication method, adsorptive spin casting. This method combines the spontaneous adsorption of PVOH at the PDMS-solution interface and the generation of ordered PVOH dewetting patterns by directional drying. PVOH is chosen because of its tunable crystallinity which will allow the study of a range of dewetting morphologies, from conventional droplets to structures with unique fractal features. Silicon wafer-supported PDMS is the substrate of choice since it will permit the probing of substrate mobility and polarity. The novelties of the research include the design of a new polymer thin-film fabrication method and the systematic exploration of relevant yet under-explored areas in polymer thin-film stability. As an educator and a female scientist in the longest-standing liberal arts college for women, the PI is committed to improving the representation and retention of women in the STEM disciplines. She will recruit and mentor a diverse group of undergraduate women to carry out new, relevant, publishable, and productive research proposed herein. With the proper structure, challenge and support, the students will gain competency and confidence for their future endeavors in the STEM fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.