Collaborative Research: Syntheses and Solution-Phase Properties of Rigid Conjugated Ladder Polymer Chains

在化学学部大分子、超分子和纳米化学项目的支持下，德州农工大学的方磊（音）和南密西西比大学的顾晓丹（音）正在准备和研究刚性棒共轭阶梯聚合物的溶液相性质。共轭聚合物是一类独特的聚合物，具有半导体性质，类似于化学元素硅，不像常用的绝缘聚合物。它们广泛用于发光器件（led）、柔性电子产品、传感器、生物医学成像和其他利用这些聚合物材料光电特性的应用。另一方面，共轭阶梯聚合物是一种双链聚合物，其键连通性类似于阶梯，因此沿着聚合物主链的重复单元都以共轭环的形式融合。与传统的单链聚合物相比，这种独特的结构赋予了共轭阶梯聚合物独特的聚合物物理性质。与该项目相关的研究将集中在聚合物-溶剂相互作用、单链构象以及一系列可溶于常见有机溶剂的共轭阶梯聚合物的链扩散动力学上。此外，合成方法将进一步发展，以控制聚合物的链长和摩尔质量的分布。这项研究有可能影响其他基础科学学科，包括合成化学、半刚性聚合物的聚合物物理学、生物大分子、聚合物加工和有机电子学。该教育计划将通过在两所大学的本科有机实验课程中实施学生进行的“诺贝尔奖反应”实验，以振兴和现代化本科化学课程。此外，顾教授还将通过实地考察和研讨会，在密西西比州历史悠久的黑人学院和大学中开展广泛的外展活动。本研究旨在发展对刚性棒共轭阶梯聚合物溶液相性质的新的基本认识。具体目标将集中在(1)设计和合成无缺陷的共轭阶梯聚合物，可以真正溶解在有机溶剂中而不聚集；(2)理解和定量聚合物-溶剂相互作用和这些模型共轭阶梯聚合物在溶液中的链构象；(3)发展基于催化剂转移聚合的可控链生长聚合方法，合成具有精确定制摩尔质量和窄分散性的共轭梯状聚合物；(4)建立共轭梯状聚合物摩尔质量与链柔韧性和扩散动力学之间的定量关联。联合合作的努力有可能推进刚性聚合物的合成化学和溶液相聚合物物理的基础知识，并为共轭阶梯聚合物的各种应用提供合理的设计原则。这些应用包括有机场效应晶体管、有机电化学晶体管、致动器、电致变色器件、光电探测器和其他光电器件。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。

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Lei Fang of Texas A&M University and Xiaodan Gu of the University of Southern Mississippi are preparing and investigating solution-phase properties of rigid-rod conjugated ladder polymers. Conjugated polymers are a unique class of polymers with semiconducting properties resembling that of the chemical element silicon, unlike commonly used insulating polymers. They are extensively used in light emitting devices (LEDs), flexible electronics, sensors, biomedical imaging, and other applications that utilize the optoelectronic property of these polymeric materials. Conjugated ladder polymers, on the other hand, are a type of double stranded polymers with the bond connectivity resembling a ladder, so that the repeating units along the polymer main chain are all fused in the form of conjugated rings. Such a unique constitution imparts a conjugated ladder polymer with distinct polymer physics properties in comparison with conventional single stranded polymers. The studies associated with this project will focus on polymer-solvent interactions, single chain conformation, as well as chain diffusion dynamics in a series of conjugated ladder polymers that are soluble in common organic solvents. Additionally, synthetic methodologies will be developed to further gain control over polymer’s chain lengths and distribution of molar masses. This research has the potential to impact other fundamental scientific disciplines, including synthetic chemistry, polymer physics for semi-rigid polymers, biomacromolecules, polymer processing, and organic electronics. The education plan will focus on revitalizing and modernizing undergraduate chemistry curricula by implementing student-performed “Nobel Prize Reaction” experiments in undergraduate organic laboratory courses at both institutions. Professor Gu will additionally conduct extensive outreach activities among historically regional black colleges and universities in Mississippi via site visits and workshops.This research will aim to develop new fundamental understandings of the solution-phase properties of rigid-rod conjugated ladder polymers. The specific objectives will focus on (1) design and synthesis of defect-free conjugated ladder polymers that can be truly dissolved in organic solvents without aggregation, (2) understanding and quantification of polymer-solvent interaction and chain conformation of these model conjugated ladder polymers in solution, (3) development of controlled chain-growth polymerization methods based on catalyst transfer polymerization to synthesize conjugated ladder polymers featuring precisely tailored molar masses and narrow dispersity, and (4) establishing quantitative correlation between molar masses of conjugated ladder polymers with chain flexibility and diffusion dynamics. The combined collaborative efforts have the potential to advance fundamental knowledge of the synthetic chemistry and solution-phase polymer physics of rigid polymers and enable rational design principles for various applications of conjugated ladder polymers. These applications include organic field effect transistors, organic electrochemical transistors, actuators, electrochromic devices, photo detectors, and other optoelectronic devices.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.