Role of Monomer Sequence and Polymer Topology in Polymer Assembly

作为非常长的分子，聚合物链可以呈现多种形状，从完全伸展到折叠。虽然一些天然聚合物（即蛋白质）的形状已经进化得非常复杂，并嵌入了重要的功能，但合成聚合物链的形状相对粗糙。因此，对链条形状的改进控制可以促进材料的设计，应用于有机电子、结构塑料和复杂流体等多种应用。最近，合成方法已经得到了改进，我们可以制造化学结构像蛋白质一样复杂的聚合物链，但设计出具有特定形状的材料的能力仍然遥不可及。从蛋白质中获得灵感，PI的团队将利用聚合物化学的这些发展来确定控制这些聚合物链形状和组装的设计规则。此外，将聚合物的分子设计与其三维形状联系起来的见解将提高我们对天然蛋白质折叠的理解，并开发出合成具有生物学固有复杂性和功能的材料所必需的工具。该项目的一个重要组成部分侧重于扩大各级对聚合物科学的参与，包括：(1)吸引即将进入社区大学的转学生参与研究工作，(2)一个强大的“科学之夜”推广活动计划，以及(3)培养本科生和研究生研究人员。第2部分：技术概述单体序列和聚合物拓扑结构是控制聚合物构象和自组装的两个基本设计处理。在克级合成序列控制多肽方面的最新进展，现在可以直接测试单体序列和聚合物拓扑控制链如何崩溃的预测，并利用以前未实现的介结构。该项目涵盖了化学模式和聚合物拓扑，作为微调材料特性的处理，因此为设计定制软材料和合成生物系统奠定了基础。除了精确定义的单体序列，连接位置和臂长，多肽还提供用户定义的链刚度，提供另一个手柄来控制链的形状和界面曲率。PI的团队将利用这个平台来探索如何利用序列和动态分子内相互作用来调整崩溃的分子结构，为蛋白质折叠和胶体设计提供见解。此外，他们将合成具有非线性拓扑结构的多肽，并研究其熔体自组装，从而消除大多数合成路线固有的分散性效应。特别是，该项目将确定界面曲率对最终形貌的作用，并探索如何将构象不对称和复杂拓扑（接枝和星形结构）结合起来微调自组装。此外，PI的团队将把多肽模型作为受控平台，以产生接枝聚合物设计的见解，从解决两个突出问题的系统开始：(1)接枝/星形/瓶刷之间的界限在哪里？(2)是否可以利用非均匀瓶刷中骨干取向之间的内在竞争来获取新的形态？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 SUMMARYAs very long molecules, polymer chains can take on many shapes ranging from fully extended to collapsed. While the shape of some natural polymers, namely proteins, has evolved to be very complex and embeds significant functionality, synthetic polymer chain shapes are comparatively crude. Improved control of chain shape could, therefore, advance the design of materials for applications as diverse as organic electronics, structural plastics, and complex fluids. Recently, synthetic methods have improved to the point where we can make polymer chains with chemistry as complex as proteins, but the ability to design materials that attain specific shape remains out of reach. Taking inspiration from proteins, the PI's group will leverage these developments in polymer chemistry to determine the design rules controlling the chain shape and assembly of these polymers. Further, insights connecting the molecular design of a polymer to its three-dimensional shape will improve our understanding of natural protein folding and develop the tools necessary to synthesize materials with the complexity and function inherent in biology. An important component of the project focuses on broadening participation in polymer science at all levels including: (1) Engaging incoming community-college transfer students in research efforts, (2) A robust program of “Science Night” outreach activities, and (3) The training of undergraduate and graduate student researchers.PART 2: TECHNICAL SUMMARYMonomer sequence and polymer topology are two essential design handles to control polymer conformation and self-assembly. Recent advances in the gram-scale synthesis of sequence-controlled polypeptoids now make it possible to directly test predictions of how monomer sequence and polymer topology control chain collapse and leverage access to previously unrealized mesostructures. This project spans both chemical patterning and polymer topology as handles for fine-tuning material properties and, thus, builds a foundation for designing made-to-order soft materials and synthetic biological systems. Beyond precisely defined monomer sequence, junction location, and arm length, polypeptoids also provide user-defined chain stiffness, offering yet another handle to control chain shape and interfacial curvature. The PI's group will use this platform to explore how sequence and dynamic intramolecular interactions can be used to tune collapsed molecular structure, providing insight on protein folding and colloid design. In addition, they will synthesize polypeptoids with non-linear topologies and study their melt self-assembly, thus eliminating the dispersity effects intrinsic to most synthetic routes. In particular, the project will determine the role of interfacial curvature on resulting morphologies and explore how conformational asymmetry and complex topologies (graft and star architectures) can be combined to fine-tune self-assembly. Further, the PI's group will model polypeptoids as controlled platforms to generate insights for graft polymer design, beginning with systems to address two outstanding questions: (1) where does the limit between graft/star/bottlebrush lie? and (2) can the inherent competition between backbone orientation in inhomogeneous bottlebrushes be used to access new morphologies?.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.