Understanding Carrier Delocalization and Transport in Micelle Forming Amphiphilic Conjugated Polymers

了解形成胶束的两亲性共轭聚合物中的载流子离域和传输

• 批准号: 2305152
• 负责人: Sarah Tolbert
• 金额: $ 80万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2305152&HistoricalAwards=false
• 关键词: Understanding; Carrier; Delocalization; Transport; Micelle

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professors Sarah H Tolbert, Benjamin J Schwartz and Yves Rubin of the University of California at Los Angeles are systematically studying assemblies of semiconducting polymers in aqueous solutions in order to seek more favorable geometries for electrical conductivity. Semiconducting polymers are an exciting class of optoelectronic materials because of their solution processability, low cost, and structural tunability. These characteristics make them useful in a range of organic electronic devices, including photovoltaics, thermoelectrics, light-emitting diodes, and transistors. However, the conformational freedom of conjugated polymers leads to intrinsic disorder that can result in poor electrical conductivity and hence limited commercial applicability. This research will address these issues and use organic synthesis, structural studies, and modern spectroscopy to explore water-soluble amphiphilic semiconducting polymers that self-assemble into cylindrical micelles as a way to straighten polymer chains and reduce defects without the need for a crystalline network. The efforts toward controlling polymer self-assembly while interrogating chain conformation with respect to carrier mobility have the potential for broad impact in the field of organic electronics and could lead to a development of new and low-cost polymeric systems for a variety of applications in which temperature and/or light are converted to electricity and vice versa. The project will provide opportunities for undergraduate and graduate students to be involved in cutting-edge interdisciplinary research. In an effort to bring the ideas of nanostructured materials, organic electronics, and self-assembly to a broader audience, experiments related to this work will be brought to secondary school classrooms throughout the greater Los Angeles area via a series of graduate-student run workshops for teachers. This research will focus on the synthesis of micelle-forming amphiphilic conjugated polymers based on poly(cyclopentadithiophene)-alt-thiophene (PCT) backbones, and will investigate of how their assembled structure controls charge mobility upon doping. In the first objective, organic synthesis and amphiphilic assembly will be used to precisely control the position of charge-balancing counterions in chemically-doped PCT polymers. PCT-based polymers with cationic, anionic, non-ionic, and zwitterionic size chains will be prepared and solution-phase small-angle X-ray scattering (SAXS) will be used to characterize micelle formation. Doping will be achieved with iron(III) salts in water and the number and nature of charge carriers will be probed using steady-state and transient IR/visible absorption spectroscopy. Based on theoretical calculations and modeling, doubly charged side chains and/or divalent solution-phase counterions will be employed to control polaron pairing into bipolarons at high doping densities. In order to create systems where the anionic side chains serve as counterions for the polarons, copolymers of anionic and either zwitterionic or non-ionic polymers will be applied. Such an approach will eliminate the need for additional ions in solution. The second objective will target new polymer backbones that are easier to chemically dope. The final goal will seek to develop methods to transition optimized assemblies from aqueous solutions into the solid state to create new materials with improved conductivity. The comprehensive approach for controlling polymer conformation and charge localization associated with this research has the potential to provide important strategies to further understand fundamental charge carrier dynamics in conjugated polymers.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.

在化学系高分子、超分子和纳米化学项目的支持下，加州大学洛杉矶分校的 Sarah H Tolbert、Benjamin J Schwartz 和 Yves Rubin 教授正在系统地研究半导体聚合物在水溶液中的组装，以寻求对导电性更有利的几何形状。 半导体聚合物因其溶液加工性、低成本和结构可调性而成为一类令人兴奋的光电材料。 这些特性使其可用于一系列有机电子器件，包括光伏、热电、发光二极管和晶体管。 然而，共轭聚合物的构象自由度会导致内在无序，从而导致导电性差，从而限制商业应用。 这项研究将解决这些问题，并利用有机合成、结构研究和现代光谱学来探索水溶性两亲性半导体聚合物，这些聚合物可以自组装成圆柱形胶束，从而无需晶体网络即可拉直聚合物链并减少缺陷。 控制聚合物自组装同时询问载流子迁移率链构象的努力可能在有机电子领域产生广泛影响，并可能导致开发用于各种应用的新型低成本聚合物系统，其中温度和/或光转换为电能，反之亦然。 该项目将为本科生和研究生提供参与前沿跨学科研究的机会。为了将纳米结构材料、有机电子学和自组装的想法带给更广泛的受众，与这项工作相关的实验将通过一系列研究生举办的研讨会带到整个大洛杉矶地区的中学课堂对于教师来说。这项研究将重点关注基于聚（环戊二噻吩）-交替噻吩（PCT）主链的胶束形成两亲性共轭聚合物的合成，并将研究它们的组装结构如何在掺杂时控制电荷迁移率。 在第一个目标中，有机合成和两亲组装将用于精确控制化学掺杂 PCT 聚合物中电荷平衡抗衡离子的位置。 将制备具有阳离子、阴离子、非离子和两性离子尺寸链的 PCT 聚合物，并使用溶液相小角 X 射线散射 (SAXS) 来表征胶束形成。 掺杂将通过水中的铁(III)盐来实现，并且将使用稳态和瞬态红外/可见吸收光谱来探测载流子的数量和性质。 基于理论计算和建模，双电荷侧链和/或二价溶液相抗衡离子将用于控制高掺杂密度下极化子配对成双极化子。为了创建其中阴离子侧链充当极化子的抗衡离子的系统，将应用阴离子与两性离子或非离子聚合物的共聚物。这种方法将消除溶液中额外离子的需要。 第二个目标将针对更容易化学掺杂的新聚合物主链。 最终目标将寻求开发方法，将优化的组件从水溶液转变为固态，以创造具有更高导电性的新材料。 与这项研究相关的控制聚合物构象和电荷局域化的综合方法有可能为进一步了解共轭聚合物中的基本载流子动力学提供重要策略。该奖项反映了 NSF 的法定使命，并通过使用基金会的评估进行评估，被认为值得支持。智力价值和更广泛的影响审查标准。