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

第一部分：非技术合成聚合物薄膜在日常生活中随处可见。通常，薄膜稳定性是理想的，例如在涂层材料的应用中。然而，受控去湿或薄膜破裂也可能是有益的，例如在印刷和其他平版印刷工艺中。现有的研究大多涉及非易失性和非极性薄膜。由挥发性和极性液体(如水)制备的聚合物薄膜的稳定性具有现实和基础意义，值得研究。本研究采用一种新的方法，即吸附旋转法，在有机硅涂层的硅衬底上制备了一种水溶性无毒聚合物--聚乙烯醇(PVOH)薄膜。这种方法允许PVOH聚合物从水中自发附着到有机硅表面，以及由于定向水蒸发而控制PVOH薄膜的破裂。这项研究将系统地研究聚合物薄膜稳定性中未被开发或未探索的领域，例如极性溶剂的(去)稳定效应、非常规薄膜破裂模式以及衬底迁移率和极性的影响。作为历史最悠久的女子文理学院的一名教育工作者和女科学家，该协会致力于提高妇女在STEM学科中的代表性和留存率。她将招募和指导一群不同的本科生女性，以开展本文提出的新的、相关的、可发表的和富有成效的研究。有了合适的结构、挑战和支持，学生们将获得在STEM领域未来努力的能力和信心。第二部分：技术总结聚合物薄膜的稳定性和受控除湿具有现实、技术和基础意义。由于在阐明干燥动力学和溶剂极性对薄膜稳定性的影响方面所涉及的特殊挑战，从水溶液中制备聚合物薄膜的研究一直受到限制。在拟议的研究中，将使用一种新的制备方法--吸附旋转铸造来研究硅片支撑的聚二甲基硅氧烷(PDMS)上的聚乙烯醇(PVOH)薄膜的脱湿。这种方法结合了PVOH在PDMS-溶液界面的自发吸附和定向干燥产生有序的PVOH除湿模式。选择PVOH是因为它的结晶度可调，这将允许研究一系列的去湿形态，从传统的液滴到具有独特分形特征的结构。硅片支持的PDMS是基板的选择，因为它将允许探测基板的迁移率和极性。研究的新颖性包括设计了一种新的聚合物薄膜制备方法，并系统地探索了聚合物薄膜稳定性的相关但未被探索的领域。作为历史最悠久的女子文理学院的一名教育工作者和女科学家，该协会致力于提高妇女在STEM学科中的代表性和留存率。她将招募和指导一群不同的本科生女性，以开展本文提出的新的、相关的、可发表的和富有成效的研究。在适当的结构、挑战和支持下，学生将获得未来在STEM领域努力的能力和信心。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.