Tactic, Ionomer, and Long Branch Length Effects in Precision Polymer Chemistry

非技术综述：世界上使用量最大的塑料是聚乙烯。它以各种形式制作，以满足今天发现的无数应用。在世界各地的发达国家，几乎每个人都会定期接触到聚乙烯。该项目的研究旨在创造类似于聚乙烯的新型聚合物，并控制和更好地了解它们的微观结构(即这些不同种类聚乙烯的分子结构)。几年来，PI的实验室开发了一种新的化学，称为admet化学，它允许以清晰、精确的方式合成一些聚合物分子并控制它们的微观结构。与几乎任何其他方法相比，使用ADMET化学可以更容易地控制微观结构。如果该项目成功，不仅可以更好地了解基础知识，还可以在性能和性能方面实现潜在的改进，这一结果将接触到世界上相当一部分人口。技术摘要：这项提议包括三个具体目标，所有这些目标都将受益于与提供互补专业知识的研究人员的合作。目标1.最具挑战性的目标将是合成取代基为甲基的精密聚合物的战术版本。目标1旨在构建具有以精确间隔连接的策略甲基的线性聚乙烯。它将试图回答这样一个问题，即这些立体中心必须相距多远才能不再影响聚合物的结晶(最终影响其机械行为)。合成策略，这是相当具有挑战性的，已经被阐明。这一概念围绕着含有两个具有甲基取代基的立体中心的单体内的C2对称性。目的2.探索精密离聚体的合成和行为。这种离聚体可以用阳离子或阴离子的聚合物主链来创建。要探讨的主要问题是，将阳离子精密聚合物与阴离子精密聚合物结合是否会产生高度有序的结构。目的3.研究聚乙烯中的长链支化现象，这一现象与LLDPE和茂金属聚乙烯的结构问题有关。具有21个碳长支链的精密聚合物将被制备。树枝之间的间距可以短到每9个碳，也可以长到每75个碳。这里的问题涉及聚合物的每个“部分”(聚乙烯主干和长链支链)将如何相互作用，例如单个长链支链将如何结晶，以及可能形成哪些新的相。

NON-TECHNICAL SUMMARY:The largest-volume plastic in use in the world is polyethylene. It is made in various forms to meet the myriad of applications found today. Almost every person in developed countries around the world encounters polyethylene on a regular basis. The research in this project is designed to create new types of polymers similar to polyethylene, and to control and better understand their microstructure (i.e., the molecular structure of these different kinds of polyethylene). Over several years new chemistry, known as ADMET chemistry, has been developed in the PI's laboratory which permits synthesis of some polymer molecules and control of their microstructure in a clear, precise manner. Microstructure can be controlled more easily using ADMET chemistry than virtually any other approach. If this project is successful, not only better fundamental understanding but also potential improvements in properties and performance could be realized, a result which would touch a significant portion of the world's population.TECHNICAL SUMMARY:Three specific objectives comprise this proposal, all of which will benefit from collaboration with researchers providing complementary expertise.Objective 1. The most challenging objective will be to synthesize tactic versions of precision polymers with the substituent being a methyl group. Objective 1 is designed to build linear polyethylene with tactic methyl groups attached at precise spacer intervals. It will try to answer the question of how far apart must these stereogenic centers be before they no longer influence crystallization of the polymer (and ultimately its mechanical behavior). The synthetic strategy, which is quite challenging, has already been elucidated. The concept revolves around C2 symmetry within a monomer containing two stereogenic centers possessing methyl substituents.Objective 2. The synthesis and behavior of precision ionomers will be probed. Such ionomers can be created with the polymer backbone being either cationic or anionic. The primary question to be probed is whether combining the cationomer precision polymer with the anionomer precision polymer will lead to highly organized structures. Special molecular interactions and the resulting morphologies will be determined.Objective 3. Long-chain branching in polyethylene will be examined, a phenomenon which relates to structural questions for LLDPE as well as metallocene polyethylene. Precision polymers possessing branches 21 carbons long will be prepared. Spacing distances between branches can be as short as every 9th carbon or as long as every 75th carbon. The question here is related to how each "part" of the polymer (the polyethylene backbone and the long-chain branch) will interact, e.g. how will the individual long-chain branches crystallize and what potentially new phases might be formed.