Organometallic Reactivity of Metal-Centered Radicals

金属中心自由基的有机金属反应性

• 批准号: 9527782
• 负责人: Bradford Wayland
• 金额: --
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-12-15 至 1998-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9527782&HistoricalAwards=false
• 关键词: Organometallic; Reactivity; Metal; Centered; Radicals

This project, funded by the Inorganic, Bioinorganic and Organometallic Chemistry program, will support Professor Bradford Wayland of the University of Pennsylvania in his continued studies of metal-centered radicals and their reactions with organic radicals, particularly in the context of olefin polymerization. Recent discoveries of new methods for establishing quasi-living polymerization in free-radical polymerization of olefins will be explored. This is accomplished through the use of metal-centered radicals to trap the growing end of the polymer. The key feature to the success of this strategy is the strength of the metal-carbon bond that is formed, which must be sufficiently weak that the reaction is rapidly reversible to allow for facile chain growth. Living radical polymerization will provide a new approach for producing low polydispersity homopolymers and block copolymers of olefins that can only be polymerized by radical initiation. The initial research will center on the use of alkyl cobalt tetramesitylporphyrin complexes to initiate and control living radical polymerization of acrylates and to provide a prototype for establishing guideline criteria for the design of metal complexes that promote similar living polymerization processes. Experiments are outlined to determine the metal-carbon bond strengths of a variety of potentially useful alkyl derivatives. The properties of polymers not only depend upon their chemical structures but also upon their molecular weight. Until recently it has been difficult to control the molecular weight and especially the dispersion of molecular weights of the individual molecules of polymers of certain types of monomers. This research explores a newly discovered way, which involves the generation of `living` polymer chains, to control the molecular weight including dispersion. The term `living` means that the individual polymer molecules are capable of adding more monomer units if they are added to the system. This allows the use of block polymerization strategies in which a second type of monomer is added to the living polymer so that a region of a new type of polymer is added to the original chain. By alternating additions of two (or more) types of monomers, polymers with new material properties that are not characteristic of those of either monomer can be prepared.

该项目由无机，生物无机和有机生物学资助， 化学计划，将支持教授布拉德福德韦兰的 宾夕法尼亚大学继续研究金属中心 自由基及其与有机自由基的反应，特别是在 烯烃聚合的背景。 最近发现的新方法， 在自由基聚合中建立准活性聚合 将对烯烃进行探索。 这是通过使用 以金属为中心的自由基来捕获聚合物的生长端。 关键 这一战略成功的一个特点是， 形成的金属-碳键必须足够弱， 该反应是快速可逆的以允许容易的链增长。 活性自由基聚合将为制备高分子材料提供一条新的途径 烯烃的低多分散性均聚物和嵌段共聚物， 只能通过自由基引发聚合。初步研究将 集中于使用烷基钴四均三甲苯基卟啉络合物， 引发和控制丙烯酸酯活性自由基聚合， 提供一个原型，以建立指导标准， 金属络合物，促进类似的活性聚合过程。 概述了确定金属-碳键强度的实验， 各种潜在有用的烷基衍生物。 聚合物的性能不仅取决于其化学结构 而且取决于它们的分子量。 直到最近， 难以控制分子量，尤其是分散 某些聚合物的单个分子的分子量 单体的种类。 这项研究探索了一种新发现的方法， 涉及“活”聚合物链的产生，以控制 分子量包括分散度。 “生活”一词的意思是， 单个聚合物分子能够加入更多的单体单元， 它们被添加到系统中。 这允许使用块 聚合策略，其中添加第二类型的单体， 活性聚合物，使得新型聚合物的区域被添加到 原来的链条。 通过交替添加两种（或多种）类型的 单体，具有新材料特性的聚合物， 可以制备具有任一单体的那些特征的聚合物。