CAREER: Employing ligand exchange reactions involving hypervalent compounds of iodine and other main-group elements in the synthesis of dynamic and functional polymers

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In this project funded by the Macromolecular, Supramolecular, and Nanochemistry Program of the Division of Chemistry, Professor Nicolay Tsarevsky of Southern Methodist University (SMU) is developing strategies for the preparation of dynamic polymers that are able to exchange their building blocks, be degraded upon chemical, light or thermal treatment, self-repair, or lock in their structures. Polymers are long chain organic molecules and are found in many facets of everyday life that utilize plastics, including food packaging, structural materials for automotive and aerospace transportation, and lightweight electronic devices. One of the main goals of materials science is to develop efficient, easy to conduct, and inexpensive methods for the preparation of well-defined polymers with predetermined structures and compositions, because these can be translated into materials for specific applications, such as self-healing materials, composites, coatings, and materials for drug delivery or tissue engineering. Professor Tsarevsky is studying how compounds that contain heavy elements form special types of chemical bonds, named hypervalent, that can easily be cleaved upon heating or irradiation with light. To broaden chemistry education, Professor Tsarevsky is developing interdisciplinary science-humanities courses; e.g. "Science on the Stage" and "Chemistry and Technology in Art: From Antiquity to the Industrial Revolution," exploring methods for general public science education, and developing a "Chemistry Summer Camp" at SMU.In this project, Professor Tsarevsky is studying how to use exchange reactions of ligands in hypervalent compounds of iodine, antimony, bismuth, selenium and tellurium [specifically- I(III), Sb(V), Bi(V), Se(IV), and Te(IV)] for the synthesis of dynamic covalent polymers, with controlled macromolecular architecture. The formation of these materials as well as their ability to exchange building blocks, to degrade and be re-assembled or self-repair, are being studied in detail. An important feature of the proposed dynamic polymers is that they have the potential to be converted to fixed structures with permanent links if and when needed. Professor Tsarevsky is also studying how these hypervalent compounds can be used to conver nucleophiles into radicals. The resulting functional radicals can react with a number of substrates, including polymers or plant oils and fatty acids with some unsaturation, and graphitic materials to yield various functional reactive materials and composites. To gain fundamental understanding of the factors that govern the kinetics and thermodynamics of the exchange reactions, as well as those of hypervalent bond homolysis, a number of model reactions are being conducted, in which structure and composition variables are being systematically varied.