Structure and Dynamics of Asymmetric Block Copolymers

非技术概述嵌段聚合物是一类将两种或多种不同化合物的物理性质联合收割机组合成单一材料的大分子。最近在了解与嵌段聚合物相关的分子尺度结构方面的进展导致了许多技术领域的创新应用，包括电池，心血管支架，用于包装和医疗保健产品的坚韧多功能塑料以及计算机芯片的制造。最近，在被称为“二嵌段共聚物”的最简单类型的此类化合物中发现了令人惊讶的纳米级分子组织的新状态，这种化合物仅包含两个端对端连接的聚合物分子。当用不对称组合物设计时，这些二嵌段共聚物形成模仿金属和合金行为的各种有序结构。该研究计划旨在揭示与这种显着的相行为相关的基本分子现象，目标是建立负责自组装软材料中低对称相（包括准晶）发展的基本原理。学生和博士后将合成有用数量的模型二嵌段共聚物，并使用一系列实验工具，包括X射线散射，电子显微镜，力学光谱和光学方法研究这些材料的结构和动力学。这项研究将同时培养聚合物领域的未来领导者，同时推进知识的基础，使嵌段聚合物的应用扩展到服务社会的无数技术先进的产品。与明尼苏达科学博物馆的合作将使公众参与材料科学和工程的令人兴奋的领域。技术概述嵌段共聚物在合成聚合物领域处于领先地位，为我们提供了无数的机会来推进我们对软材料的基本理解，同时解决了与材料科学和工程相关的各种学科的无数技术应用。最近的进展与二嵌段共聚物，最简单的分子结构，在这一类的自组装材料，已经暴露了非凡的新概念，有序和无序的限制，不对称的分子结构，导致形成离散的，名义上的球形颗粒。该项目概述了一个雄心勃勃的实验计划，旨在揭示负责形成四面体紧密堆积的弗兰克-卡斯珀相和准晶体在二嵌段共聚物熔体的基本原理。模型材料将以几乎单分散的形式合成，并使用小角X射线散射和电子显微镜进行结构表征。控制相变动力学的分子输运现象将使用时间分辨技术进行评估，包括小角中子散射，光学方法和动态力学光谱。该计划将建立控制低对称相形成的原则，作为纯嵌段共聚物和共混物中分子结构、分散性、组成和构象不对称性以及分子量的函数。该奖项反映了NSF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。

NON-TECHNICAL SUMMARYBlock polymers are a class of macromolecules that combine the physical properties of two or more different compounds into a single material. Recent advances in understanding the molecular-scale structure associated with block polymers has led to innovative new applications in numerous areas of technology including batteries, cardiovascular stents, tough versatile plastics for use in packaging and health care products, and manufacturing of computer chips. Surprising new states of nanoscale molecular organization have recently been discovered in the simplest type of such compounds known as "diblock copolymers", which contain just two polymer molecules linked end-to-end. When designed with an asymmetric composition these diblock copolymers form a variety of ordered structures that mimic the behavior of metals and alloys. This research program aims to uncover the fundamental molecular phenomena associated with this remarkable phase behavior, with the goal of establishing the basic principles responsible for the development of low-symmetry phases including quasicrystals in self-assembled soft materials. Students and post docs will synthesize useful quantities of model diblock copolymers and investigate the structure and dynamics of these materials using a host of experimental tools including X-ray scattering, electron microscopy, mechanical spectroscopy, and optical methods. This research will simultaneously train future leaders in the field of polymers while advancing the fundamental base of knowledge enabling expanded application of block polymers to myriad technologically advanced products that serve society. A collaboration with the Science Museum of Minnesota will engage the public in the exciting field of materials science and engineering. TECHNICAL SUMMARYBlock copolymers command a leading position in the field of synthetic polymers, offering innumerable opportunities to advance our fundamental understanding of soft materials while addressing myriad technological applications across various disciplines associated with materials science and engineering. Recent advances with diblock copolymers, the simplest molecular architecture in this category of self-assembling materials, have exposed extraordinary new concepts regarding order and disorder in the limit of asymmetric molecular architectures leading to the formation of discrete, nominally spherical particles. This project outlines an ambitious experimental program designed to uncover the basic principles responsible for the formation of tetrahedrally close-packed Frank-Kasper phases and quasicrystals in diblock copolymer melts. Model materials will be synthesized in nearly monodisperse form and characterized structurally using small-angle X-ray scattering and electron microscopy. The molecular transport phenomena that govern phase transition dynamics will be assessed using time-resolved techniques including small-angle neutron scattering, optical methods and dynamic mechanical spectroscopy. This program will establish the principles that govern the formation of low symmetry phases as a function of molecular architecture, dispersity, compositional and conformational asymmetry, and molecular weight in pure block copolymers and blends.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.