In this project funded by the Chemical Catalysis Program (CAT) of the Division of Chemistry (CHE), Professor Christopher Hobbs of Sam Houston State University (SHSU) works with undergraduate and graduate students to develop new and recyclable chemical catalysts. Chemical catalysts increase the speed of chemical reactions. Catalysts are commonly used for preparing important materials such as plastics and medicines. It is desirable to make catalysts with long lives to avoid the high costs and environmental problems associated with the metallic elements that are often used. In this research, polymers supports ("plastic backbones") are used to recover a catalyst from a reaction so it can be re-used. Varied separation strategies are developed, depending on the polymer support. In much the same way that oil separates from water, the polymer-supported catalysts developed by Professor Hobbs and his students are "phase-selective" so they physically separate from the products after facilitating a chemical reaction. This green chemistry approach avoids wasteful and time-consuming purification steps. Educational aspects of this project are aimed at broadening the scope of polymer science education at SHSU through the development of new experiments for laboratory courses as well as hands-on participation in the research lab by undergraduates. Additional societal benefits include the recruitment and participation of under-represented students (high school, undergraduate, and graduate) in research projects and volunteer work as math and science tutors in the Windham School District, the public-school system for those incarcerated in the Texas Department of Criminal Justice (TDJC).
Professor Hobbs and his students develop new polymer-supported ligands and catalysts which are nonpolar and phase-selectively soluble. These polymer-supported catalysts are prepared using a combination of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) polymerization, and atom transfer radical polymerization (ATRP). These are all techniques that offer high levels of control over polymer architecture. Specific goals of the project target polymer-supported salen, N-heterocyclic carbene (NHC), and N-heterocycle-based ligands and catalysts. Professor Hobbs is further preparing the first examples of phase-selective single chain nanoparticle (SCNP) and unimolecular ligand/initiator system (ULIS) supported catalysts. Because of their non-polar phase selectivity, these catalysts may be recovered and recycled under simple liquid/liquid separation conditions, thus avoiding chromatographic purifications. The ability to remove and recycle diminishes solvent waste and highlights the implications of this project as a model for green and sustainable chemistry. Broader impacts of this work include recruitment of students from under-represented groups to STEM (science, technology, engineering and mathematics) careers, as well as promoting outreach and volunteerism aimed at individuals who are incarcerated in the Texas Department of Criminal Justice (TDJC) System.
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.
