Structure and Dynamics of Asymmetric Block Copolymers

非技术性聚合嵌段聚合物是一类将两种或两种以上不同化合物的物理性质结合成一种材料的大分子。在了解与嵌段聚合物相关的分子结构方面的最新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。最近在一种被称为“两嵌段共聚物”的最简单的化合物中发现了令人惊讶的纳米级分子组织的新状态，这种化合物只包含两个端到端相连的聚合物分子。当设计具有不对称组成时，这些两嵌段共聚物形成各种有序结构，模仿金属和合金的行为。这项研究计划旨在揭示与这种非凡的相行为相关的基本分子现象，目的是建立负责自组装软材料中包括准晶在内的低对称相发展的基本原理。学生和博士后将合成大量有用的模型两嵌段共聚物，并使用包括X射线散射、电子显微镜、机械光谱和光学方法在内的一系列实验工具来研究这些材料的结构和动力学。这项研究将同时培养未来聚合物领域的领导者，同时推进基础知识基础，使嵌段聚合物能够扩大应用于无数服务于社会的技术先进产品。与明尼苏达州科学博物馆的合作将使公众参与到令人兴奋的材料科学和工程领域。技术综述嵌段共聚物在合成聚合物领域处于领先地位，提供了无数机会增进我们对软材料的基本理解，同时解决与材料科学和工程相关的各种学科的无数技术应用。两嵌段共聚物是这类自组装材料中最简单的分子结构，其最新进展揭示了关于不对称分子结构极限中的有序性和无序性的非凡新概念，导致了离散的名义上的球形粒子的形成。该项目概述了一个雄心勃勃的实验计划，旨在揭示在两嵌段共聚物熔体中形成四面体紧密堆积的Frank-Kasper相和准晶的基本原理。模型材料将以近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对其结构进行表征。支配相变动力学的分子传输现象将使用时间分辨技术进行评估，包括小角中子散射、光学方法和动态机械光谱。该计划将建立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相对分子质量的函数来管理低对称相形成的原则。该奖项反映了NSF的法定使命，并通过使用基金会的智力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.