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

第一部分： 聚合物在日常生活中是有价值的材料。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，使制造智能手机的微电子产品成为可能。该项目研究混合聚合物刷，即一种以上的聚合物链连接到一个表面。与其他聚合物系统相比，聚合物刷的独特特征在于它们结合到表面，垂直于表面延伸，并且具有受控的厚度和受控的表面化学。我们将研究两种刷子的混合物如何相分离，如油和水，并形成比当今先进的图案化方法更小的结构。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，我们将探索作为新的纳米结构，作为新的能量存储材料和作为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。该研究计划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，并培养学生在协作环境中工作。研究生将反过来作为导师和榜样，从康奈尔大学和其他大学的本科生，同时获得监督技能。来自其他学校的REU学生强调代表性不足的学生将在夏季参加研究。PI和研究生志愿者将在RET项目和教师研讨会中与高中教师互动。 第二部分： 技术概要本基础研究计划将研究混合聚合物刷的合成、加工和表征，该混合聚合物刷设计成在刷膜的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Kumada化学合成。研究了具有可控刷均匀性的致密刷的面内相分离过程。研究将利用新的二元刷引发剂开发使用Passerini化学形成线圈型均聚物，二嵌段共聚物和多嵌段共聚物混合刷。的相行为，以及它如何比较计算预测将研究均聚物和嵌段共聚物对的目标是创造稳定的周期性结构。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。为了实现我们的目标，在这些刷层的均匀长程有序，我们将研究溶剂蒸气退火和热瞬态激光尖峰退火结合引导结构。刷子的表征将使用各种分析方法，包括X射线反射计，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。电荷输运测量将进行新的棒-线圈混合刷。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.