Studies of Mixed Polymer Brushes Designed for Periodic In-Plane Order

第 1 部分：非技术摘要 聚合物是日常生活中有价值的材料。这些长链分子是从食品包装到医疗器械制造再到我们穿的衣服等行业的基础。聚合物是纳米技术革命的关键组成部分，能够制造微电子产品，从而使智能手机成为可能。该项目研究混合聚合物刷，即不止一种聚合物链附着在表面上。与其他聚合物系统相比，聚合物刷的独特之处在于它们与表面结合，垂直于表面延伸，并且具有受控的厚度和受控的表面化学性质。我们将研究两个刷子的混合物如何像油和水一样相分离，并如何通过当今先进的图案化方法形成比可能更小的结构。在几纳米的长度尺度上，表面的性质可以从刚性的无机结构转变为柔软的有机结构。计算机模型预测对称的周期性结构，我们将探索这些结构作为新的纳米结构、新的储能材料和生物技术应用的新材料。 我们将与计算机专家合作，通过提供有关他们的概念如何正确预测这些新的混合刷涂层的信息来改进他们的理论和模型。该研究项目将使学生参与聚合物科学和材料研究，培养具有全球意识的研究生，并培训学生在协作环境中工作。研究生将成为康奈尔大学和其他大学本科生的导师和榜样，同时获得监督技能。来自其他学校（重点是代表性不足的学生）的 REU 学生将在夏季参与研究。 PI 和研究生志愿者将在 RET 项目和教师研讨会上与高中教师互动。 第 2 部分：技术摘要 该基础研究计划将研究混合聚合物刷的合成、加工和表征，该混合聚合物刷旨在在刷膜平面中形成受控的周期性间距。通过使用线圈-线圈和棒-线圈结构的混合聚合物刷并利用它们的面内相分离，我们将创建具有受控形貌、孔隙率或多路径传输特性的图案化结构。混合聚合物刷将使用柔性线圈聚合物的活性自由基聚合和共轭棒聚合物的熊田化学来合成。将研究具有受控刷均匀性的致密刷的面内相分离过程。研究将利用帕塞里尼化学开发的新型二元刷引发剂来形成线圈型均聚物、二嵌段共聚物和多嵌段共聚物混合刷。将研究均聚物和嵌段共聚物对的相行为及其与计算预测的比较，目的是创建稳定的周期性结构。通过我们的合作，计算材料科学将用于指导刷子的设计和选择，预测物理结构并帮助检查这些新材料的物理特性。为了实现这些刷层中均匀长程有序的目标，我们将研究溶剂蒸气退火和热瞬态激光尖峰退火以及引导结构。将使用各种分析方法对刷子进行表征，包括 X 射线反射法、掠入射 (GI) SAXS 和 WAXS、中子反射率和 STORM 超分辨率荧光显微镜测量。电荷传输测量将在新的杆线圈混合刷上进行。每种技术都将提供有关材料内部或表面组织的信息，并有助于我们理解所产生的结构。

PART 1: NON-TECHNICAL SUMMARY Polymers are valuable materials in everyday life. These long-chain molecules are the basis of industries ranging from food packaging to medical device manufacture to the clothing we wear. Polymers are critical components in the nanotechnology revolution enabling the manufacture of microelectronics that make possible smart phones. This project studies mixed polymer brushes, that is, more than one kind of polymer chain tied to a surface. Unique features of polymer brushes compared to other polymer systems are that they are bound to a surface, extended perpendicular to the surface, and have a controlled thickness and controlled surface chemistry. We will study how mixtures of two brushes phase separate, like oil and water, and form structures smaller than possible with today's advanced patterning methods. Over length scales of a few nanometers the nature of a surface can be transformed from a rigid inorganic structure to one that is soft and organic. Computer models predict symmetrical, periodic structures that we will explore as new nanostructures, as new energy storage materials and as new materials for biotechnology applications. We will work with computer experts to improve their theory and models by providing information about how well their concepts correctly predict these new mixed brush coatings. The research program will engage students in polymer science and materials research, foster globally aware graduate students and train students to work in a collaborative environment. Graduate students will in turn serve as mentors and role models to undergraduate students from Cornell and other universities, while gaining supervisory skills. REU students from other schools with an emphasis on underrepresented students will participate in research during the summer months. The PI and graduate student volunteers will interact with high school teachers in an RET program and teachers' workshops. PART 2: TECHNICAL SUMMARY This fundamental research program will investigate the synthesis, processing and characterization of mixed polymer brushes designed to form controlled periodic spacings in the plane of the brush film. By using mixed polymer brushes of coil-coil and rod-coil architectures and harnessing their in-plane phase separation we will create patterned structures with controlled topography, porosity or multipath transport properties. Mixed polymer brushes will be synthesized using living radical polymerization of flexible coil polymers and Kumada chemistry of conjugated rod polymers. The in-plane phase separation process of dense brushes with controlled brush uniformity will be investigated. Studies will make use of new binary brush initiators developed using Passerini chemistry to form coil-type homopolymer, diblock copolymer and multiblock copolymer mixed brushes. The phase behavior and how it compares to computational predictions will be studied for homopolymer and block copolymer pairs with the goal of creating stable periodic structures. Computational materials science through our collaborations will be used to guide brush design and selection, to predict physical structure and to aid examination of the physical properties of these new materials. To achieve our goal of uniform long-range order in these brush layers, we will investigate solvent vapor annealing and thermal transient laser spike annealing in conjunction with guiding structures. Characterization of the brushes will be made using a variety of analytical methods including X-ray reflectometry, grazing incidence (GI) SAXS and WAXS, neutron reflectivity and STORM superresolution fluorescence microscopy measurements. Charge transport measurements will be carried out on new rod-coil mixed brushes. Each technique will provide information about the internal or surface organization of the material and will aid our understanding of the structures produced.