Controlled Radical Synthesis in Supercritical Carbon Dioxide of New Stimuli-Responsive Materials for Biomedical Applications

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In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Rebecca Braslau of the University of California at Santa Cruz will study heterogeneous nitroxide-mediated radical polymerization (NMRP) in super-critical carbon dioxide and will synthesize well-defined stimuli-responsive materials. This project is a three-way international collaboration with Prof. Fawaz Aldabbagh of the National University of Ireland in Galway and Prof. Carlos Elvira of the Institute of Polymer Science & Technology in Madrid, Spain. Nitroxide-based initiators bearing polar or fluorophilic functionalities (perfluoroalkyl and polysiloxane groups) on the nitroxide moiety will be synthesized. During polymerization this nitroxide moiety will be used to control the partitioning of the growing polymer in super-critical carbon dioxide, such that both monomer and alkoxyamine initiator are initially soluble but the polymer precipitates at a critical degree of polymerization. The addition of a stabilizer will permit control of the final particle size. The development of polymeric alkoxyamines that possess dual initiator and stabilizer capabilities for dispersion NMRP in super-critical carbon dioxide will be explored. Thermal or pH-responsive polymers will be developed for applications such as drug-delivery, non-viral gene vectors and surface coatings for cell manipulations. These designed materials will be examined in biocompatibility studies, complexation studies with DNA, as well as plasmid transfection levels using different cell lines. The broader impacts include training graduate students and enhancing infrastructure for research and education through the establishment of a trilateral international collaboration. The synergistic interactions between the American, Irish and Spanish groups will further broaden the training of these students, introducing a multicultural enrichment while promoting learning, teaching and training of young scientists in an international, collaborative environment. This project will provide further scientific understanding about using green polymerization conditions for industrial synthesis. Carbon dioxide is a ubiquitous atmospheric gas, and its use as a solvent for plastic material manufacturing could lead to a reduction in volatile organic compound (VOC) emissions. The project would also further our understanding of the basic design principles for polymers used in biomedical applications.