CAREER: An Integrated Approach to Understanding and Controlling the Self-Assembly of Rod-Coil Block Copolymers with an Educational Program in Materials Exploration

技术概述：本提案旨在对功能性棒-线圈嵌段共聚体系的自组装热力学和动力学有基本的了解。这项工作具有特别重要的意义，因为棒-线圈嵌段共聚物在有机光电和生物应用中的优化已经被提出，而对其自组装性能的预测是走向应用的必要步骤。例如，最近在这些材料的器件物理方面的突破表明，两种不同功函数的导电有机物之间的界面的纳米级结构在分离电子和空穴以获取光伏电池中的电压方面发挥了不可或缺的作用，或者反过来在产生光所需的复合中起到了不可或缺的作用。嵌段共聚物模板技术的直接应用因以下事实而变得复杂：经典研究使用的是高斯链形状的模型聚合物，这些聚合物不参与液晶相互作用。虽然在棒-线圈嵌段共聚体系中观察到了许多新的结构，但控制自组装的热力学目前尚不清楚。初步证明，Segalman基团是一个弱分离的棒-线圈嵌段共聚体系，随着温度的升高，从片状相到向列相再到各向同性相转变，同时遵循聚合物的标度关系。这种独特的模型系统为探索平衡热力学提供了一个难得的机会。控制这种自组装的热力学参数，包括嵌段共聚物的分离强度、棒-棒相互作用和分子几何结构将被研究。薄膜结构是技术上最相关的，我们将寻求对薄膜限制对棒-线圈嵌段共聚物的影响的理解。职业研究的目标是(I)了解棒块对嵌段共聚自组装热力学的影响，(Ii)开发控制这些具有重要技术价值的材料的薄膜自组装的方法，以及(Iii)通过将拟议的研究与正在进行的各级学生教育活动相结合，培养更广泛的人群对聚合物科学的兴趣。非技术综述：棒-线圈嵌段共聚物在许多最近优化有机光电子器件、生物膜和药物输送应用的努力中发挥着核心作用。所有这些努力的关键是理解控制具有非经典相互作用的聚合物中纳米级自组装的热力学。随着对功能嵌段共聚物的纳米级图案化的控制，这项工作有望对这一广泛的应用和社区产生重大影响。此外，结构-财产关系是儿童如何发展对周围环境的理解的核心。一个全面的教育计划将利用这种与生俱来的好奇心，向广泛的学生介绍聚合物科学和上文讨论的研究。一名高中物理教师和首席研究员将开发一套动手探索模块，帮助高中新生理解科学的跨学科性质。然后，这些单元将通过与探索学院教师学院的讲习班向更广泛的年轻学生群体传播，该学院培训全国教师队伍。研究成果还将用于改善本科生的聚合物教育，并使本科生和研究生都能接触到涉及自组装聚合物的研究。国际学生还将定期访问该实验室，让该小组接触到现代研究的跨学科和国际性。

TECHNICAL SUMMARY: This proposal seeks to contribute fundamental understanding regarding the thermodynamics and kinetics of self-assembly of functional rod-coil block copolymer systems. This work is of particular importance since rod-coil block copolymers have been suggested in the optimization of organic optoelectronic as well as biological applications, and a predictive understanding of their self-assembling properties is a necessary step towards application. For instance, recent breakthroughs in the device physics of these materials have demonstrated that the nanometer scale structure of interfaces between two conducting organics of different work function play an integral role in the separation of electrons and holes to harvest voltage in a photovoltaic cell or conversely in the recombination necessary to generate light. Direct application of block copolymer templating techniques is complicated by the fact that classical studies employed model polymers with Gaussian chain shape that did not participate in liquid crystalline interactions. While a number of novel structures have been observed in rod-coil block copolymer systems, the thermodynamics which control self-assembly are currently unclear. Preliminarily, the Segalman group has demonstrated a weakly segregated rod-coil block copolymer system which transitions from lamellar to nematic to isotropic phases with increasing temperature while following polymeric scaling relationships. This unique model system provides an exceptional opportunity to probe equilibrium thermodynamics. The thermodynamic parameters which control this self-assembly including the block copolymer segregation strength, rod-rod interaction, and molecular geometry will be investigated. The thin film architecture is the most technologically relevant, and an understanding of the effects of thin film confinement on rod-coil block copolymers will be sought. The CAREER research goals are to (i) understand the effect of a rod-block on the thermodynamics of block copolymer self-assembly, (ii) develop methods for controlling thin film self-assembly of these technologically important materials, and (iii) to foster an interest in polymer science in a broader population by integrating the proposed research with ongoing educational activities for students at various levels. NON-TECHNICAL SUMMARY: Rod-coil block copolymers play a central role in many recent efforts to optimize organic optoelectronic devices, biological membranes, and drug delivery applications. Critical to all of these efforts is an understanding of the thermodynamics that control nanometer-scale self-assembly in polymers with non-classical interactions. This work is expected to have a significant impact on this broad range of applications and communities as control is gained over the nanoscale patterning of functional block copolymers. Furthermore, structure-property relationships are at the core of how children develop an understanding of their surroundings. A comprehensive educational plan will harness this innate curiosity to introduce a broad spectrum of students to polymer science and to the research discussed above. A high school physics teacher and the principal investigator will develop a set of hands-on exploratory modules that will help high school freshmen understand the interdisciplinary nature of science. These modules will then be disseminated to a broader, younger group of students through workshops with the Exploratorium Teacher Institute which trains a national pool of teachers. The research results will also be employed to improve undergraduate polymer education and to expose both undergraduate and graduate students to research involving self-assembling polymers. International students will also routinely visit the laboratory to expose the group to the cross-disciplinary and international nature of modern research.