Polymers are ubiquitous in our everyday lives. They are plastics, rubbers or gels, and in living systems they serve a structural role as proteins, and also the source of genetic information as DNA and RNA. Small chemical units (monomers) are linked together to produce a polymer with any number of desired functions. The characteristics of the polymer are determined both by the monomer, and how the monomer units are connected. Professor Grubbs at the California Institute of Technology in Pasadena, CA develops new methods for producing polymers, specifically on developing new types of polymers with complex structures which generate new materials for important commercial and academic uses. One important approach involves very long polymer chains where the ends are connected, so that the resulting cyclic polymer does not have a beginning or end. These polymers are challenging to produce. Many theories suggest cyclic polymers will have different properties than identical polymers where the ends are not connected. Polymers with enhanced properties are anticipated to result from this work. This project provides an excellent platform for research training of scientists and helps to prepare a skilled workforce for academia and industry.
Ring-opening metathesis polymerization (ROMP) is a critical tool in polymer synthesis and is used to produce numerous model systems, as well as a number of commercial materials. Most of the work to date in Professor Grubbs' group utilizes homogeneous catalysts that are easy to control and are manipulated to produce well-defined polymeric structures. Although less common, heterogeneous catalysts are also used to provide new materials. In one case, the catalyst is covalently linked to a silica support in such a way that cyclic polymers are selectively produced. The heterogeneous system maintains the cyclic structure of the polymer throughout the reaction, and releases the cyclic polymer from the support, which provides a simple way to separate the product from the catalyst. The resulting high molecular weight hydrocarbon polymers provide model materials for verification of a variety of theoretical predictions. Additionally, large-scale synthesis of such material enables previously unrealized commercial applications. Another novel strategy uses a monomer which is introduced in the gas-phase to a heterogeneous system, which produces polymers with different properties than those formed in solution. This method provides hydrocarbon polymers which are not accessible using homogeneous catalysts.
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.
