CAREER: Multiscale Assembly of Conjugated Polymers at Dynamic Reconfigurable Interfaces

非技术概要电活性材料的受控组装一直是电子和能源工业的基石。近年来见证了半导体聚合物的激增，它有望从柔性电子产品和透明太阳能电池到难以察觉的医疗设备的各种应用。然而，控制半导体聚合物从分子到器件尺度的组装仍然是一个核心挑战，这将严重影响其器件性能。本研究通过开发动态的、可重新配置的界面来解决这一挑战，以指导半导体聚合物的组装成跨长度尺度的高度有序结构。阐明表面定向聚合物组装的基本机理，指导这种界面的设计。这种方法受到生物矿物（例如骨）形成方式的启发，与传统方法形成对比，传统方法采用高度有序的刚性表面来指导电子材料的组装。这项工作最终可能使高性能、低成本的印刷电子、能源和生物医学设备与人体和生活环境无缝交互，这将对电子、能源和医疗保健行业产生影响。考虑到表面定向组装在制造各种功能材料方面的广泛适用性，从计划工作中获得的基本见解可以进一步扩展到半导体聚合物以外的领域。该项目的教育活动与研究部分相结合，旨在缩小美国高科技劳动力需求不断增长与STEM教育有限招生之间的差距。高分子科学和电子学一直处于高科技产业的中心舞台。总体目标是通过公众参与、教育推广、本科和研究生教育，吸引、培养和留住STEM人才，尤其是女性。本研究旨在阐明从分子到厘米尺度界面驱动共轭聚合物组装的基本机制，并开发一种新的动态模板方法来实现具有规定顺序和控制性能的聚合物组装。虽然已知共轭聚合物的多尺度形态（分子构象/堆积、中尺度畴尺寸/取向、宏观尺度结晶度/排列）可以在数量级上调节电子、光学和机械性能，但将共轭聚合物组装成跨多个长度尺度的高度有序结构仍然是一个核心挑战。该项目将更好地理解半刚性给受体共轭聚合物的组装机制，它与已被充分研究的柔性聚合物具有不同的组装行为。计划的工作集中在这一领域的一个特别重要的问题上：考虑到薄膜在溶液沉积过程中表面诱导成核的优势，阐明界面在指导共轭聚合物组装中的作用。将这项工作与以前的研究区分开来的一个关键方面是关注动态的、可重构的接口。这种方法的灵感来自于生物系统中普遍存在的动态合作组合，这种组合需要最小的能量输入来获得跨越长度尺度的精致结构。使用假设驱动的方法，本研究将通过基于成核理论的自由能建模来补充原位多尺度结构表征，为动态、可重构界面的聚合物组装提供新的基本见解。这项研究将从根本上对大分子组装产生新的见解，这是材料研究的核心课题。由于自由能势垒较低，许多聚合物组装过程发生在界面上，而表面定向组装过程的机制却鲜为人知；这是这项工作最终要解决的一个挑战。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 SUMMARYControlled assembly of electrically active materials has been a cornerstone to the electronics and energy industries. Recent years have witnessed a surge of semiconducting polymers which promise diverse applications from flexible electronics and transparent solar cells to imperceptible medical devices. However, it remains a central challenge to control the assembly of semiconducting polymers from the molecular to the device scales, which critically impact their device performance. This research addresses this challenge by developing dynamic, reconfigurable interfaces to direct the assembly of semiconducting polymers into highly ordered structures across length scales. The fundamental mechanism of surface-directed polymer assembly will be elucidated to guide the design of such interfaces. This approach, inspired by how biominerals (e.g. bone) are formed, is in contrast to conventional approaches wherein highly ordered, rigid surfaces are employed to direct assembly of electronic materials. This work may ultimately enable high-performance, low-cost printed electronic, energy and biomedical devices in forms that seamlessly interact with the human body and the living environment, which would have impact on the electronic, energy and healthcare industries. The fundamental insights from the planned work can be further extended to areas beyond semiconducting polymers, given the broad applicability of surface-directed assembly to the manufacturing of a wide range of functional materials. The educational activities of the project are integrated with the research component, aiming at narrowing the gap between increasing demand in high-tech workforce and limited enrollment in STEM education in the US. Both polymer sciences and electronics have been at the center stage of high-tech industries. The overarching goal is to attract, nurture and retain STEM talents, particularly women, through public engagement, educational outreach, undergraduate and graduate education. TECHNICAL SUMMARYThis research aims to elucidate the fundamental mechanisms of interfacially-driven assembly of conjugated polymers from the molecular to centimeter scale, and to develop a new dynamic templating approach to achieve polymer assemblies with prescribed order and controlled properties. Although it is known that the multiscale morphology of conjugated polymers (molecular conformation/packing, mesoscale domain size/orientation, macroscale crystallinity/alignment) can modulate the electronic, optical, and mechanical properties by orders of magnitude, it remains a central challenge to assemble conjugated polymers into highly ordered structures across multiple length scales. This project will provide better understanding of the assembly mechanism of semi-rigid donor-acceptor conjugated polymers, which exhibit distinct assembly behavior from the well-studied flexible polymers. The planned work focuses on a particularly important problem in this area: to elucidate the role of interfaces in directing conjugated polymer assembly, considering the predominance of surface-induced nucleation during thin-film deposition from solution. A key aspect that distinguishes this work from previous research is the focus on dynamic, reconfigurable interfaces. This approach is inspired by dynamic, cooperative assemblies ubiquitous in biological systems, which require minimal energy input to attain exquisite structures across length scales. Using a hypothesis-driven approach, this research will provide new fundamental insights on polymer assembly at dynamic, reconfigurable interfaces by complementing in-situ multiscale structural characterizations with free-energy modeling based on nucleation theory. This study will lead to fundamentally new insights on macromolecular assembly -- a subject at the heart of materials research. Many polymer assembly processes take place at interfaces due to generally lower free energy barriers, whereas the mechanism of surface-directed assembly process is much less understood; this is a challenge that this work ultimately addresses.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.