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

非技术总结：世界上使用量最大的塑料是聚乙烯。 它以各种形式制成，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其微观结构（即，这些不同种类的聚乙烯的分子结构）。 几年来，PI的实验室开发了新的化学，称为ADMET化学，它允许合成一些聚合物分子并以清晰，精确的方式控制其微观结构。 使用ADMET化学比几乎任何其他方法都更容易控制微观结构。 如果该项目获得成功，不仅可以更好地理解基本原理，还可以实现性能和性能的潜在改进，其结果将触及世界人口的很大一部分。技术概要：该提案包括三个具体目标，所有这些都将受益于与研究人员的合作，提供补充专业知识。目标1.最具挑战性的目标将是合成具有甲基取代基的精密聚合物的战术版本。 目的1是设计用于构建具有以精确间隔基连接的有规甲基的线性聚乙烯。 它将试图回答这样一个问题，即这些立体中心在它们不再影响聚合物的结晶（并最终影响其机械行为）之前必须相距多远。 合成策略，这是相当具有挑战性的，已经阐明。 这个概念围绕着C2对称性的单体含有两个立体中心具有甲基取代基。 精密离聚物的合成和行为将被探索。 这样的离聚物可以用阳离子或阴离子的聚合物主链产生。 要探讨的主要问题是，将阳离子型精密聚合物与阴离子型精密聚合物结合是否会导致高度有序的结构。 特殊的分子相互作用和由此产生的形态将被确定。 聚乙烯中的长链支化将被检查，一种与LLDPE以及茂金属聚乙烯的结构问题有关的现象。 将制备具有21个碳长的支链的精密聚合物。 分支之间的间隔距离可以短至每9个碳或长至每75个碳。 这里的问题涉及聚合物的每个“部分”（聚乙烯主链和长链分支）将如何相互作用，例如，各个长链分支将如何结晶以及可能形成哪些潜在的新相。

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.