GOALI: Polymerization Catalysis, Block Copolymers, and Nuclear Magnetic Resonance Characterization of Polylactide

点击翻译按钮获取中文摘要

9815854HillmyerThis joint project between the University of Minnesota (UM) and Cargill Dow Polymers LLC (CDP) is funded by the Division of Materials Research and the Office of Multidisciplinary Activities of the Directorate for Mathematical and Physical Sciences. The research effort will be focused on three interconnected areas related to the preparation and analysis of biodegradable polylactide (PLA) homopolymers, copolymers, and blends. The first area of research will center on the commercially relevant tincatalyzed polymerization of lactide. Currently, the precise mechanism of polymerization in many tin-based systems is unclear, and control of the polymerization processes can be difficult. New tin catalysts will be designed, synthesized, and examined with the aim of producing a controlled polymerization of lactide. Novel tin catalysts with well-defined ligand environments and predictable reactivities will be prepared and characterized. These complexes will ultimately be useful for the preparation of macromolecules with controlled chemical and morphological characteristics. Secondly, PLA-containing block copolymers and blends will be examined with emphasis on rubber toughening and crystallization phenomena in hybrid composites of PLA and rubbers such as polyisoprene. These new copolymers and blends will be designed to unveil critical structure/property relationships that can ultimately be used to enhance the mechanical properties of commercial PLA while retaining its biodegradation characteristics. In the final area of research, solid-state and solution nuclear magnetic resonance (NMR) spectroscopy will be employed for the characterization of PLA and novel PLA-containing materials. The research will focus on a detailed understanding of the PLA crystal structure and environment through the use of specifically labeled. PLA materials. Experiments that definitively correlate PLA tacticity with the corresponding resonances in the NMR spectra will also be performed. The NMR assignments that result will be used to correlate the selectivity of various catalysts to the tacticity of the polymer.%%%The research described in this proposal is focused on PLA, a commercially viable biodegradable polymer. Research and development in the field of biodegradable polymers are extremely important endeavors due to the nation's problems with waste disposal and to environmental pressures associated with traditional commodity plastics. Currently, most biodegradable polymers do not compete effectively with commercially useful polymers from a mechanical performance perspective. A clear need exists for new polymers that possess biodegradable properties as well as mechanical, thermal, and processing characteristics comparable to conventional polyolefins, such as polypropylene, or other thermoplastics like polystyrene. In an effort to meet these challenges, CDP (a joint venture between Cargill Incorporated and the Dow Chemical Company) has developed technology to produce PLA at a cost competitive with traditional plastics. The manufacturing process begins with cornstarch and ends with high-molecular-weight polymer that is fully degradable in a compost environment and has physical properties similar to those of polystyrene. However, PLA suffers from mechanical property deficiencies that have hindered its wide spread use. Fundamental investigations of the chemistry and materials science of PLA are of paramount importance to address these deficiencies and will ultimately result in polymers with superior properties compared to existing PLA. These advances will lead to a broader scope of applications for biodegradable polymers and will lessen the need for environmentally unfriendly materials. This joint project between industry and academia is poised to impact future generations of PLA-based materials. In addition, the collaboration includes graduate student internships in industry that will allow students to appreciate the importance of biodegradable materials from an industrial perspective.***