CAREER: Visualizing single-chain conformation and dynamics of bottlebrush polymers in the bulk state

在我们的日常生活中，聚合物的应用几乎无处不在。经过几十年的研究，由于聚合物链的典型尺寸太小，直接看到单个聚合物分子的形状以及它在自然环境中的运动方式几乎是不可能的。这个项目使用下一代光学技术——超分辨率显微镜来实现直接成像单个聚合物在固体状态下的行为。虽然这些技术已经在几个生物应用中进行了探索，以实现几十纳米的分辨率，但它们在材料科学中的应用却非常有限。这项工作将集中在一种叫做瓶刷的特殊聚合物上，它已经引起了光子材料和药物输送的兴趣，并且恰好是一个完美的尺寸，可以被超分辨率成像。该项目将直接解决单个聚合物的结构和行为如何与日常长度尺度下材料的特性相联系的问题。除了提供的基本理解之外，它还将使新材料的有效设计具有社会效益。此外，超分辨率显微技术在材料科学领域的进一步应用，将使该领域的其他人更容易采用这些方法来解决自己的研究问题。为配合纳米科技和材料科学的主题，本计划亦会支援青少年科学社的新课程发展。青少年科学社是一项面向3至5年级弱势青少年的课外活动。校园内的研究生和志愿者每周将在新的6-8周的模块中指导学生，这些模块将公开提供，并准备被其他提供类似项目的人采用。技术总结：单链行为和宏观性质之间的联系是我们对聚合物物理的现代理解的中心原则。然而，单聚合物的直接可视化是困难的，特别是在应用相关的配置中，因为单聚合物链的尺寸通常是纳米级的。该项目解决了在块状材料中成像单链聚合物的构象和动力学的巨大挑战。实验将利用超分辨率显微镜，它可以在几十纳米分辨率下成像结构，既非侵入性，又通过荧光标记具有化学特异性。本研究中特定的聚合物是瓶刷，探索体与先前稀释溶液结果的构象刚性，并直接可视化纠缠动力学。这里提出的问题可以通过单链的可视化直接回答，而其他技术，如散射、流变学和模拟只能间接地探索这些问题。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。

NON-TECHNICAL SUMMARYPolymers are used everywhere in our daily lives in almost every application imaginable. After decades of research, it is still nearly impossible to directly see the shape of a single polymer molecule and how it moves in its native environment, because the typical sizes of polymer chains are too small. This project uses the next generation of optical techniques called super-resolution microscopy to achieve this goal of directly imaging how single polymers behave in the solid state. While these techniques have been explored in several biological applications for achieving tens of nanometer resolutions, their use in materials science has been much more limited. This work will focus on a specific class of polymers called bottlebrushes, which have attracted interest for photonic materials and drug delivery, and happen to be a perfect size to be imaged by super-resolution. This project will directly address the question of how the structure and behavior of single polymers connect to the properties of the material at everyday length scales. Beyond the fundamental understanding that this offers, it will also enable efficient design of new materials for societal benefit. In addition, the further application of super-resolution microscopy to materials science will make it easier for others in this community to adopt these methods to their own research problems. In line with this theme of nanotechnology and materials science, this project will also support new curriculum development for Junior Science Club, an afterschool activity for underrepresented youths of grades 3-5. Graduate students and volunteers across campus will mentor students weekly over new 6-8 week modules, which will be publicly available and ready for adoption by others offering similar programs. TECHNICAL SUMMARYThe connection between single-chain behavior and macroscopic properties is a central tenet in our modern understanding of polymer physics. However, direct visualization of single polymers is difficult particularly in application-relevant configurations, because single polymer chains are typically nanometers in size. This project tackles the grand challenge of imaging the conformation and dynamics of single polymer chains within a bulk material. The experiments will utilize super-resolution microscopy, which can image structures at tens of nanometer resolution, both non-invasively and with chemical specificity through fluorescent labeling. The specific polymers in this study are bottlebrushes, exploring the conformational rigidity in the bulk vs. previous dilute solution results, and directly visualizing entanglement dynamics. The questions posed here can be directly answered by visualization of single chains, while other techniques such as scattering, rheology, and simulation can only probe these questions indirectly.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.