CAS: Responsive Macromolecules by Wavelength Controlled Vinyl Ketone Photopolymerization and Photodegradation

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With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Dominik Konkolewicz of Miami University is employing radical photopolymerization to prepare well-defined and photodegradable polymers made of vinyl ketones. Polyvinyl ketones are a class of polymers that are widely used not only as components for packaging materials and agricultural films, but also as functional plastics in applications such as imaging, microfabrication and sensors. An interesting feature of these polymers is that they can be degraded to their low-molecular weight fragment upon exposure to UV irradiation, making them ideally suitable for recycling. This research will focus on investigating chemical mechanisms of radical photopolymerization and photodegradation of a diverse range of vinyl ketones. The gained mechanistic insights will then be used to develop photo-gated plastics that are prepared under visible light and degrade under ultraviolet irradiation. Broader impacts from the project will involve the development and implementation of outreach activities that engage middle and high school students. Through the polymer chemistry and polymer materials science and engineering divisions of the American Chemical Society, the project will engage members of the polymer chemistry community by developing educational resources through the macromolecular alliance for community resources and outreach (MACRO), as well as webinars. The project will also provide training and mentoring of graduate and undergraduate students of diverse backgrounds. Undergraduate students from underserved groups will be recruited and mentored through engagement with the Louis Stokes Alliance for Minority Participation (LSAMP), with a specific focus on preparing LSAMP students for research through first year research experience project.Vinyl ketones are unique photoactive monomers leading to polymers that have distinct photo-responsive properties. However, the full potential and broad use of vinyl ketones has been hindered in part due to incomplete understanding of monomer reactivity and underlying polymerization mechanisms. This research will study the mechanism of radical generation in vinyl ketone photopolymerization and photodegradation. The developed methodology could offer unique opportunities for vinyl ketones in reversible addition–fragmentation chain transfer (RAFT) polymerization to enable access to diverse functional groups. Detailed mechanistic studies will also be performed to address challenges in atom transfer radical polymerization (ATRP) of vinyl ketones and further understand pathways toward efficient polymerization of these complex monomers. Furthermore, using these mechanistic insights into the polymerization of vinyl ketones, photochemical polymerization induced self-assembly (photoPISA) and photochemical degradation induced modifications of self-assembly (photoDIMSA) will be performed to promote and modulate the self-assembly of polymers. The DIMSA approach could impact the polymer self-assembly broadly, as well as targeted delivery in stimulus responsive polymers. If these studies are successful, new additive manufacturing and 3D printing technologies could result, enabled by orthogonal light responsiveness, with one wavelength of light synthesizing advanced polymeric structures, and the other wavelength adding complexity by post-polymerization degradation on selected regions.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.