CAREER: Multiscale Assembly of Conjugated Polymers at Dynamic Reconfigurable Interfaces

电活性材料的非技术性组装一直是电子和能源行业的基石。近年来，半导体聚合物出现了激增，它们有望实现从柔性电子产品、透明太阳能电池到隐形医疗设备的各种应用。然而，控制半导体聚合物从分子尺度到器件尺度的组装仍然是一个核心挑战，这对其器件性能有着至关重要的影响。这项研究通过开发动态的、可重新配置的界面来解决这一挑战，以引导半导体聚合物组装成跨长度尺度的高度有序结构。将阐明表面定向聚合物组装的基本机制，以指导此类界面的设计。这种方法受到生物矿物(例如骨)形成方式的启发，与传统方法不同，传统方法使用高度有序的刚性表面来指导电子材料的组装。这项工作可能最终实现高性能、低成本的印刷电子、能源和生物医学设备，其形式与人体和生活环境无缝互动，这将对电子、能源和医疗行业产生影响。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，从计划中的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，旨在缩小高科技劳动力需求增加与美国STEM教育招生人数有限之间的差距。聚合物科学和电子学都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、本科生和研究生教育来吸引、培养和留住STEM人才，特别是妇女。技术综述本研究旨在阐明共轭聚合物从分子到厘米尺度的界面驱动组装的基本机理，并开发一种新的动态模板方法来实现具有指定顺序和可控性质的聚合物组装。虽然已知共轭聚合物的多尺度形态(分子构象/堆积、介观结构域大小/取向、大尺度结晶度/取向)可以在数量级上调节电子、光学和力学性质，但将共轭聚合物组装成多个长度尺度上的高度有序结构仍然是一个核心挑战。这个项目将使我们更好地理解半刚性供体-受体共轭聚合物的组装机理，它表现出与已有研究的柔性聚合物不同的组装行为。计划中的工作集中在这一领域的一个特别重要的问题上：考虑到从溶液中沉积薄膜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。这项工作与以前的研究不同的一个关键方面是对动态、可重新配置接口的关注。这种方法的灵感来自于生物系统中普遍存在的动态、合作的组装，这种组装只需要最少的能量输入就可以获得跨越长度尺度的精致结构。利用假设驱动的方法，这项研究将通过基于成核理论的自由能模型补充原位多尺度结构表征，为聚合物在动态、可重构界面上的组装提供新的基本见解。这项研究将导致对大分子组装的全新见解--这是材料研究的核心课题。由于自由能垒普遍较低，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则知之甚少；这是这项工作最终解决的挑战。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.