Design, Structure, and Properties of Polymeric Materials with Programmed Macromolecular Architectures

本研究项目将从金属合金相冶金学的基本原理和一些最基本的生物学原理（如同手性）中汲取灵感，并将其应用于具有简单和复杂结构（可能包括记忆效应）的单个大分子的设计和合成，这将允许在复杂的聚合物材料中发现新的概念。预计这些概念将与目前生物学中最有效的方法相竞争。这项工作的结果有望促进对太阳能电池、包括药物输送在内的医疗设备的新工具、聚合物材料的环境方面和其他用途等应用感兴趣的超分子电子特性的控制。本研究涉及有机、大分子和超分子化学、物理学、生物学、合成生物学和材料科学之间的交叉学科；它还包括与来自世界各地的科学家的合作。该计划还将使本科生和研究生、高中生和博士后科学家的教育成为可能。第2部分：技术概述Frank-Kasper相最早被发现并应用于金属合金中。在软物质中，它们是在一个相关的NSF项目中发现的，最近在嵌段共聚物、表面活性剂和其他组装物中也发现了它们。预计它们将很快演变成新的技术应用。然而，许多超分子球形组件是螺旋的，因此是手性的，分子机制以及同手性在这些相中的作用仍有待了解。记忆效应在这些材料中产生的结构和性质只能通过手性超分子树状大分子和其他单分散组装体来实现。因此，该项目将阐明手性在Frank-Kasper软相中的作用，并将为聚合物和任何其他有机材料的新材料性能的开发奠定基础。尽管大多数聚合物和有机材料表现出螺旋结构，因此是手性的，但当它们由非手性或外消旋构建块组装时，它们被认为是外消旋的，并显示出低有序的结构和性能。这种超分子倾向类似于等规（同手性）、同规（异手性）和无规（外消旋）聚合物。一种新的结晶机制，即不考虑手性的齿轮机制，最近被发现，并被证明有可能消除手性和外消旋构建块产生的螺旋结构的完美性差异。将研究这种机制对外消旋和非手性构建块的组合产生与同手性构建块相同的材料性质的通用性。这项研究的结果将对许多类型的材料产生广泛的科学影响，包括电子、医疗和其他应用。这个项目的另一个方面涉及到单分散聚合物。含有单维物种的单分散聚合物只能由生物学产生。这项研究将包括继续发展自中断活性聚合，这将使研究真正的单分散聚合物与标准活性聚合产生的窄分散聚合物的结构和性能之间的异同成为可能。这些也将影响涉及具有许多潜在应用的聚合物材料设计的广泛领域。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYThis research program will draw inspiration from a combination of fundamental principles derived from the metallurgy of metal alloy phases and some of the most fundamental principles of biology such as homochirality, and apply them to the design and synthesis of individual macromolecules with simple and complex architectures that may include memory effects, which will allow to discover new concepts in complex polymeric materials. These concepts are anticipated to be competitive with the most efficient methodologies currently available in biology. The outcome of this work is expected to facilitate control of supramolecular electronic properties of interest for applications such as solar cells, new tools for medical devices including drug delivery, environmental aspects of polymer materials, and other uses. This research involves an interdisciplinary program at the interface between organic, macromolecular and supramolecular chemistry, physics, biology, synthetic biology, and materials science; it also includes collaborations with scientists from around the world. This program will also enable the education of undergraduate and graduate students, high-school students, and postdoctoral scientists.PART 2: TECHNICAL SUMMARYThe Frank-Kasper phases were first discovered and employed in metal alloys. In soft matter they were discovered in a related NSF program and recently also in block-copolymers, surfactants and other assemblies. They are expected to evolve soon into new technological applications. However, many supramolecular spherical assemblies are helical and therefore chiral and the molecular mechanism as well as the role of homochirality in these phases remains to be understood. The structures and properties generated by memory effects in these materials are accessible only by chiral supramolecular dendrimers and by other monodisperse assemblies. Therefore, this project will elucidate the role of chirality in Frank-Kasper soft phases and will be fundamental for the development of new material properties from polymers and any other organic materials.Even though most polymeric and organic materials exhibit helical structures and are therefore chiral, they are considered to be racemic when assembled from achiral or racemic building blocks and display low-ordered structures and properties. This supramolecular trend is similar to that of isotactic (homochiral), syndiotactic (heterochiral), and atactic (racemic) polymers. A new mechanism of crystallization, the cogwheel mechanism that disregards chirality, has recently been discovered and shown to be potentially able to eliminate the difference regarding the perfection of helical structures generated from chiral versus racemic building blocks. The generality of this mechanism to combinations of racemic and achiral building blocks to generate the same material properties as the homochiral ones will be studied. The outcome of this research will have broad scientific impact across many types of materials, including electronic, medical, and other applications.Another aspect of this project involves monodisperse polymers. Monodisperse polymers containing single-dimension species are produced only by biology. This research will include continued development of self-interrupted living polymerization, which will enable study of similarities and differences between the structure and properties of truly monodisperse polymers versus those of narrow dispersity produced by standard living polymerizations. These will also impact broad areas involving the design of polymeric materials with numerous potential applications.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.