Collaborative Research: Electrospray Deposition of 'Melting Gels' for Multifunctional Coatings

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Silica glass has been valued more than 2000 years for its optical properties and chemical and thermal stability, making it a natural candidate for surface coatings. Current methods, such as chemical vapor deposition or conventional sol-gel processing, often require energy-costly high vacuum or high temperature methods. This collaborative project seeks to couple innovations in a new class of sol gel materials, 'melting gels', with electrospray deposition to create materials-efficient, durable hybrid glass coatings. Melting gels transform into these hybrid glasses at low temperatures enabling the use of substrates that would not normally be considered, such as polymer webs that are key for continuous manufacturing. The combination with electrospray, a type of industrially-accepted electrostatic manufacturing technology, enables thin (microscale) coatings on complex three-dimensional surfaces with facile incorporation of additives in ambient processing conditions. This award contributes fundamental understanding of the key process settings and the resulting coating properties (e.g. mechanical, electrical, chemical, and/or biological) that are desirable for a wide variety of coating applications. Results from this research benefits industrial applications in aerospace, nautical, automotive, and medical implant sectors, which would benefit U.S. economy. This project provides opportunities for students from a smaller Hispanic-serving institution and a major research institution to collaborate and engage in multidisciplinary research. Melting gels are oligomeric silsesquioxane materials made by a sol-gel process that possess consolidation temperatures in the range of 120 to 170 degree C, where the melting gels decompose and crosslink into an irreversible hybrid organically-modified silica network. Melting gels and their hybrid glass partners are synthesized using a soft-chemistry approach that allows for direct covalent bonding of organic moieties to the inorganic network. Electrospray deposition, a means of delivering uniform charged microdroplets in a high electric field, provides the necessary dynamic control of the micro- to nano-scale structure of melting gels to achieve superior coating properties. However, the effects of the charge injection and polarity of the spray on the sol-gel are currently unknown. This research varies these parameters along with the melting gel consolidation temperature and intrinsic charge to identify changes in the consolidation mechanism through primarily mechanical and spectroscopic analysis. These effects are then be connected to the final performance of the coatings. The team for this grant consists of two partners, combining sol-gel chemistry and electrospray deposition expertise to create a holistic approach for synthesis, processing, and property characterization.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.