Living Polyisonitrile Polymerization Catalysts

在有机动力学计划的支持下，Novak博士将研究有机金属催化剂的设计、制备和实施，这些催化剂用于已知可产生稳定的螺旋聚合物的单体的“活性”聚合。具体地说，将研究用于异腈聚合的新型镍(I)和镍(II)催化剂。将进行详细的机理研究，以努力提供必要的信息，以针对具体应用修改这些新催化剂。诺瓦克博士研究的基本前提是，有机金属络合物具有多种配位球和氧化态，可以用来以可预测的方式和高度精确地改变聚合物内基的反应性。根据特定反应的要求，可以要求有机金属物种激活或去活聚合物端基。诺瓦克博士的研究旨在提供一种方法，通过这种方法，除了导致聚合物形成的所需引发和传播步骤外，端基可以对所有过程不起反应。%用于控制合成定义明确的大分子的最终聚合催化剂是“活的”。活性聚合可用于合成具有预定分子量、窄链长分布和限定端基的大分子。此外，生命系统允许精确合成“嵌段共聚物”，它提供了简单聚合物混合物或无规共聚物无法获得的一系列性能组合。诺瓦克博士将利用这种方法控制合成聚异腈，聚异腈是一类重要的可溶性聚合物。此外，他的方法的生物性将被用于制备新型的二嵌段和三嵌段共聚物，这是一种新的热塑性弹性体。

With support from the Organic Dynamics Program, Dr. Novak will investigate the design, preparation, and implementation of organometallic catalysts for the "living" polymerization of monomers known to yield stable, helical polymers. Specifically, new Ni(I) and Ni(II) catalysts for the polymerization of isonitriles will be investigated. Detailed mechanistic studies will be performed in an effort to provide the information necessary to modify these new catalysts for specific applications. The basic premise of Dr. Novak's study is that organometallic complexes, which possess versatile coordination spheres and oxidation states, can be used to alter the reactivity of polymer endgoups in a predictable manner and with a high degree of precision. Depending upon the requirements of the particular reaction, the organometallic species may be called upon to either activate or deactivate the polymer endgroup. Dr. Novak's study is designed to provide a means by which endgroups can be rendered unreactive toward all processes other than the desired initiation and propagation steps that lead to polymer formation. %%% The ultimate polymerization catalysts for the controlled synthesis of well-defined macromolecules are "living". Living polymerizations can be used to synthesize macromolecules with pre-determined molecular weights, narrow chain-length distributions, and defined endgroups. In addition, living systems allow the precise synthesis of "block copolymers", which offer a combination of properties unobtainable from simple polymer blends or random copolymers. Dr. Novak will utilize this approach for controlled synthesis of polyiso- nitriles, an important class of soluble polymers. In addition, the living nature of his approach will be exploited in the preparation of novel di- and tri-block copolymers, which are of interest as a new class of thermoplastic elastomers.