Iterative Macromolecular Functionalization

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Rebekka Klausen of Johns Hopkins University is developing a single synthetic platform that will access macromolecules that cannot be made by direct polymerization of traditional feedstocks. Chemical transformations will first be utilized to prepare polymers and copolymers containing carbon-boron bond along the main backbone. The synthesized macromolecules will then be diversified by converting these bonds to corresponding alcohols, chlorides and simple alpha-olefins. The synthesis of these historically inaccessible polymers is expected to uncover new structure-function relationships and enable systematic evaluation of physical, mechanical, and chemical properties of these systems. Additionally, since the prepared polymers will contain polar and nonpolar functionalities, improved adhesion and oxygen permeability is expected. Both properties are very important in several applications or relevance to commercial plastics. The involvement in the Summer Undergraduate Research Excellence (SURE) program between Johns Hopkins University and Trinity Washington University, a minority-serving institution and women’s college in Washington, DC, will enable training of minority and first-generation undergraduate students in polymer science research. Additional outreach and educational activities related to polymer science and sustainability will be conducted at a college preparatory high school with a diverse student body in Olney, Maryland. This project will focus on the development of new polymer modification chemistries using borane-substituted polyolefins as precursors to access (co)polymers that are otherwise difficult to obtain. Specifically, the synthesis of copolymers that are formally derived from allylic monomers such as allyl chloride and allyl alcohol, as well as propene, will be conducted using Matteson homologation followed by hydrogenative, oxidative, and/or chlorinative deborylation. The insertion of a methylene or chloromethyl group into a carbon–boron bond via Matteson homologation is a particularly compelling application of organoborane chemistry because it can be applied iteratively and stereospecifically, while yielding few byproducts. This research is targeting (co)polymers of allyl alcohol, allyl chloride, and alpha-olefins; polymers that are elusive and highly desired materials that cannot be accessed directly from polymerization of allylic monomers due to competitive chain transfer, catalyst poisoning, or mismatched reactivity ratios. Polymers synthesized as a result of this work is anticipated to open up new chemical space for systematic structure-property studies of relevance to the synthetic organic and polymer communities. 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.