CAREER: Functional Polymer Surfaces and Networks via Thiol-Click Chemistry

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TECHNICAL SUMMARY: Recent advances in synthetic polymer chemistry have resulted in numerous fundamental scientific discoveries that have enabled the development of materials with unique and useful properties. Among notable discoveries, "click" chemistry and the ensuing "Robust, Efficient, Orthogonal" strategies are revolutionizing our ability to tailor-make polymeric materials with specific function. This CAREER proposal leverages a specific class of click reactions - "thiol-click" - to tackle unexplored areas in polymer surface engineering and hybrid polymer networks that will lead to unprecedented control of surface functionality and a novel set of functional glassy polymer networks. The research objectives of this CAREER proposal are three fold: 1) design "reactive inkjet" and scanning-near field lithography strategies that exploit high efficiency thiol-click reactions for multicomponent, precision engineered surfaces 2) synthesize and gain fundamental understanding of a new class of hybrid polymer networks via orthogonal thiol-click/benzoxazine chemistries, and 3) fundamentally investigate polybenzothiazines as a new class of thiol-containing thermosets. Towards achieving these objectives, the following specific research directives are proposed. 1) Surface Engineering via Thiol-Click Reactions: The PI will develop thiol-click reactions for the design and fabrication of patterned, multicomponent polymer surfaces. Orthogonal strategies involving radical-mediated thiol-yne and base-catalyzed thiol-isocyanate, thiol-epoxide and thiol-bromo enable advancements in surface engineering. Exploitation of high efficiency thiol-click reactions with "reactive inkjet" and "wet" near-field lithography will provide the ability to investigate nanoscale chemical reactions at surfaces under mild, biologically relevant conditions. 2) Dual-Crosslink Thiol-Click/Benzoxazine Hybrid Networks: Using thiol-click reactions, the PI will design and prepare a unique class of dual crosslinked polymer networks comprising a primary thiol-ene network which templates a sequential secondary polybenzoxazine network. Aside from unique network architectures, the sequential nature of network synthesis offers opportunities to provide fundamental knowledge of network formation and structure in glassy polymeric materials. 3) Synthesis of Novel Polybenzothiazine Networks: A new class of thiol-containing thermoset polymers derived from bis(1,3-benzothiazine) monomers will be synthesized. Sister to polybenzoxazines, these polymers comprise a thiophenol/Mannich-bridge backbone and exhibit properties substantially different from polybenzoxazines. The influence of hydrogen bonding on network structure and thermomechanical properties will be elucidated. NON-TECHNICAL SUMMARY: The proposed research offers a robust strategy for the fabrication of multifunctional polymer surfaces and hybrid polymer networks using highly efficient, orthogonal chemistries. Successful implementation of this research will provide access to functional surfaces and networks that will facilitate advancements in areas such as 1) sensors, microfluidics, and "smart" self-cleaning, antifouling surfaces and 2) polymer composite matrices, adhesives, and high temperature coatings. The educational objective of this CAREER is to implement an integrated, discovery-driven education platform that promotes polymer science and diversity from K - Graduates. A significant outreach program is proposed comprising 1) a teacher development workshop for a school district comprising 92% underrepresented minorities, 2) a high school job shadow/research experience program, and 3) an undergraduate engagement program that aims to attract/retain polymer science majors. Graduate students involved in each of the above outreach activities will be given frequent opportunities to integrate research activities to grow interest in polymer science for K - UG students. Graduate students will be trained and educated in technologically relevant areas via a comprehensive, multilevel approach involving synthesis-advanced characterization-modeling strategies. The ultimate outcome of this integrated K - Graduate education and research platform is to provide a large socio-economic impact by 1) encouraging a diverse population of students to pursue careers in scientific disciplines and 2) by providing the fundamental understanding of polymer surface engineering and networks necessary to establish the shortest paths between scientific discovery and exploratory applications.