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

9815854Hillmyer明尼苏达大学(UM)和嘉吉陶氏聚合物有限责任公司(CDP)的这个联合项目由材料研究部和数学和物理科学局多学科活动办公室资助。研究工作将集中在三个相互关联的领域，与生物可降解聚乳酸(PLA)均聚物、共聚物和共混物的制备和分析有关。第一个研究领域将集中在丙交酯的商业催化聚合上。目前，在许多锡基体系中，聚合的确切机理尚不清楚，聚合过程可能很难控制。将设计、合成和检验新的锡催化剂，目的是生产丙交酯的受控聚合。具有明确的配体环境和可预测的反应活性的新型TiN催化剂将被制备和表征。这些络合物最终将用于制备具有可控化学和形态特征的大分子。其次，将考察含有聚乳酸的嵌段共聚物和共混物，重点研究聚乳酸和橡胶(如聚异戊二烯)混杂复合材料中的橡胶增韧和结晶现象。这些新的共聚物和共混物将旨在揭示关键的结构/性能关系，这些关系最终可用于增强商业聚乳酸的机械性能，同时保持其生物降解特性。在最后的研究领域，固体和溶液核磁共振波谱将用于聚乳酸和新型聚乳酸材料的表征。这项研究将重点放在通过使用特定的标记来详细了解解放军的晶体结构和环境。解放军材料。还将进行将聚乳酸的规整性与核磁共振谱中的相应共振相关联的实验。结果将用于将各种催化剂的选择性与聚合物的规整性相关联。%本提案中描述的研究重点是聚乳酸，一种商业上可行的可生物降解聚合物。由于国家在废物处理方面的问题以及与传统商品塑料相关的环境压力，可生物降解聚合物领域的研究和开发是极其重要的努力。目前，从机械性能的角度来看，大多数可生物降解的聚合物并不能有效地与商业用途的聚合物竞争。显然需要具有生物可降解性以及可与传统的聚烯烃(如聚丙烯)或其他热塑性塑料(如聚苯乙烯)相媲美的机械、热和加工特性的新聚合物。为了应对这些挑战，CDP(嘉吉公司和陶氏化学公司的合资企业)开发了生产聚乳酸的技术，其成本与传统塑料具有竞争力。制造过程以玉米淀粉开始，以高分子量聚合物结束，这种聚合物在堆肥环境中完全可降解，具有与聚苯乙烯相似的物理性质。然而，聚乳酸的机械性能缺陷阻碍了其广泛应用。对聚乳酸的化学和材料科学的基础研究对于解决这些不足至关重要，并最终将导致与现有的聚乳酸相比具有更好的性能的聚合物。这些进展将导致可生物降解聚合物的更广泛的应用范围，并将减少对环境友好材料的需求。这一产业界和学术界的联合项目将对未来几代解放军材料产生影响。此外，合作还包括研究生在工业领域的实习，这将使学生从工业的角度认识到可生物降解材料的重要性。

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.***