Development of More Active and More Selective Catalysts for ATRP

化学系的大分子、超分子和纳米化学项目获得该奖项，支持卡内基梅隆大学的Krzysztof Matyjaszewski教授开发用于原子转移自由基聚合(ATRP)的新型铜基催化剂。自由基聚合是一种化学反应，它按顺序添加小分子单体，形成由数百或数千个重复单元组成的长聚合物链。这种强大的合成方法被用来制造近一半的塑料，全球每年约有1亿吨。ATRP是一种特殊类型的自由基聚合，可以制备具有精确控制链长和形状的先进聚合物。ATRP还被用来通过将合成聚合物与生物分子和无机颗粒表面进行化学连接来制备各种杂化材料。Matyjaszewski教授的团队为这种重要的ATRP过程开发了新的催化剂，具有更高的活性和选择性。这项研究将有助于创造更精确的聚合物和扩大可聚合单体的范围，同时使用较低水平的催化剂。通过使用“绿色”ATRP催化剂，这项研究提供了环境改善的聚合条件，与聚合物的工业生产相关。更广泛的影响包括对本科生和研究生进行聚合物科学方面的培训，以及通过教学网页和视频教育公众关于受控自由基聚合的知识。在这一领域，Matyjaszewski教授和他的团队将探索制备比原始ATRP催化剂活性高得多的催化剂，这些催化剂在抑制铜诱导的终止和转移反应的同时保持对ATRP途径的选择性。ATRP是在氧化还原活性过渡金属络合物的催化下，在休眠的卤代烷和正在生长的自由基之间进行可逆的原子转移过程。ATRP用于制备具有明确结构的先进聚合物。它们包括均匀的直链，也包括星形、梳形和环状聚合物，以及统计、周期、梯度和嵌段共聚物。新的ATRP催化剂是基于三(吡啶甲基)胺或四氮杂大环家族的配体。新配合物的热力学和动力学性质将通过电化学、光谱和计算方法来确定，以建立全面的结构/反应关系。正在开发的新催化剂将用于(甲基)丙烯酸酯和(甲基)丙烯酰胺的ATRP，也用于ATRP活性较低的单体，如乙烯基酯和N-乙烯基酰胺。将评估这些催化剂以F-C、N3-C、SCN-C键激活烷基(伪)卤化物的能力，这些键的活性比ATRP中通常使用的烷基溴化物或氯化物低得多。极具活性的铜基催化剂不仅与烷基卤化物反应，而且还与扩散的自由基反应，形成瞬时有机铜物种。后一种顺磁性化合物诱导终止过程。因此，将对铜催化终止的机理进行详细的研究，以深入了解更具选择性的催化剂的设计和优化聚合条件。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With this award, the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division is supporting Professor Krzysztof Matyjaszewski at Carnegie Mellon University to develop new Cu-based catalysts for atom transfer radical polymerization (ATRP). Radical polymerization is a chemical reaction that sequentially adds small molecules of monomers to form long polymer chains that consist of hundreds or thousands of repeating units. This powerful synthetic method is used to make nearly half of all plastics, about 100 million tons worldwide each year. ATRP is a special type of radical polymerization that can prepare advanced polymers with precisely controlled chain lengths and shapes. ATRP is also used to prepare various hybrid materials by chemically linking synthetic polymers to biomolecules and to surfaces of inorganic particles. Professor Matyjaszewski’s team develops new catalysts for such important ATRP processes with enhanced activity and selectivity. This study will contribute to the creation of more precise polymers and expansion of range of polymerizable monomers, while using diminished levels of catalyst. By employing “green” ATRP catalysts, this research provides environmentally improved polymerization conditions, relevant for the industrial production of polymers. The broader impacts include the training undergraduate and graduate students in polymer science and educating the public about controlled radical polymerization via instructional webpages and videos.Under this ward, Professor Matyjaszewski and his team will explore preparation of catalysts with much higher activity than the original ATRP catalysts and that retain selectivity for the ATRP pathway while suppressing Cu-induced termination and transfer reactions. ATRP is based on a reversible atom transfer process between dormant alkyl halides and growing radicals, catalyzed by redox active transition metal complexes. ATRP is used to prepare advanced polymers with well-defined architecture. They include uniform linear chains and also star, comb and cyclic polymers, as well as statistical, periodic, gradient and block copolymers. The new ATRP catalysts are based on ligands belonging to the tris(pyridylmetyl)amine, or tetra-aza-macrocycle families. Thermodynamic and kinetic properties of new complexes will be determined through electrochemical, spectroscopic and computational methods to establish the comprehensive structure/reactivity relationship. The new catalysts being developed will be employed for ATRP of (meth)acrylates and (meth)acrylamides and also for less ATRP-active monomers such as vinyl esters and N-vinylamides. The catalysts will be evaluated for their ability to activate alkyl (pseudo)halides with F-C, N3-C, SCN-C bonds, much less active species than the alkyl bromides or chlorides that are typically used in ATRP. The extremely reactive Cu-based catalysts react not only with alkyl halides but also with propagating radicals, forming transient organocuprate species. The latter paramagnetic compounds induce termination processes. Therefore, the mechanism of Cu-catalyzed termination will be studied in great detail to gain insight into the design of more selective catalysts and optimize polymerization conditions.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.