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Title:Functional electrospun fibers for responsive coatings and sacrificial templates
Author(s):Doan, Thu Q.
Director of Research:Sottos, Nancy R.
Doctoral Committee Chair(s):Sottos, Nancy R.
Doctoral Committee Member(s):White, Scott R.; Kilian, Kristopher; Evans, Christopher M.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Core-shell fibers
Sacrificial templates
Electrospun fibers
Self-healing coatings
Smart coatings
Responsive coatings
Abstract:Accumulated damage can degrade material properties, such as conductivity in batteries, strength in composites, and barrier effectiveness of coatings. Self-healing materials have the ability to repair or prevent further damage autonomously, where and when it occurs. Autonomous repair can increase the lifetime of materials, thereby reducing the economic and environmental impact of material damage and degradation. A successful strategy for designing self-healing materials relies on microencapsulation of liquid healing agents which are dispersed throughout a bulk polymer or coating. In this work, we explore the use of electrospun core-shell fibers to sequester healing chemistry for protective coatings. In coaxial electrospinning, two immiscible liquids are pumped through the inner (self-protective core) and outer (polymer shell wall) coaxial needles. A high voltage is applied on the needle tips to electrostatically draw out core-shell fibers (submicron size in diameter). We have developed a polysiloxane based coating for steel containing two types of core-shell fibers. When the coating is mechanically damaged, the two fiber types release their liquid core materials to fill the damaged region, crosslink, and restore the protective coating layer. Characterization of fibers and coating include SEM, TEM, confocal fluorescence microscopy, and FTIR. A self-healing system containing amine and epoxy chemistry is also developed and some advantages and limitations of electrospinning are discussed. Development of new coatings synthesized by core-shell electrospinning will provide corrosion protection to metals, thus increasing material lifetime and performance. Another popular self-healing strategy is using microvasculature. Microvascular systems employ channels to deliver liquid healing agents to damage sites. One method of fabricating microchannels is embedding a degradable fiber into a polymeric matrix or composite and removing the fiber (through chemical or thermal processing) to create a channel. In this research, we study two polymer systems for use as sacrificial templates for developing microvasculature. Poly(lactic acid) and cyclic poly(phthalaldehyde) fibers are electrospun, embedded into epoxy, and thermally or chemically decomposed to remove the fiber and create channels. Characterization of the fibers and their resultant channels include SEM, TGA, and confocal fluorescence microscopy. Successful evacuation and filling of channels with fluid is confirmed for both polymer systems in different epoxy systems. Finally, a frontal ring-opening metathesis polymerization system with Grubbs’ 2nd generation ruthenium catalyst and cyclic poly(phthalaldehyde) is developed, where concurrent polymerization of bulk polymer and decomposition of sacrificial material to produce vasculature is demonstrated.
Issue Date:2017-11-22
Rights Information:Copyright 2017 Thu Q. Doan
Date Available in IDEALS:2018-03-13
Date Deposited:2017-12

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