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

第一部分：非技术概述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各种行业的基础。聚合物是纳米技术革命中的关键部件，使制造微电子成为可能，使智能手机成为可能。这个项目研究的是混合聚合物刷子，即绑在一个表面上的一种以上的聚合物链。与其他聚合物系统相比，聚合物刷子的独特特征是它们结合在表面上，垂直于表面延伸，并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是如何像油和水一样相分离的，并形成比今天先进的图案化方法所能形成的更小的结构。在几个纳米的长度范围内，表面的性质可以从刚性的无机结构转变为柔软和有机的结构。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子涂层的信息来改进他们的理论和模型。该研究项目将吸引学生从事聚合物科学和材料研究，培养具有全球意识的研究生，并培养学生在合作环境中工作。研究生反过来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。来自其他学校的REU学生，重点是代表人数不足的学生，将在夏季几个月参与研究。PI和研究生志愿者将在RET计划和教师研讨会上与高中教师互动。第二部分：技术概述这个基础研究项目将研究混合聚合物刷子的合成、加工和表征，这些刷子被设计成在刷子膜平面上形成受控的周期性间隔。通过使用线圈-线圈和杆-线圈结构的混合聚合物刷子，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。柔性线圈聚合物的活性自由基聚合和共轭棒状聚合物的Kumada化学将合成混合聚合物刷子。研究了电刷均匀度可控的致密电刷的面内相分离过程。研究将利用利用帕塞里尼化学开发的新型二元刷子引发剂来形成盘状均聚物、两嵌段共聚物和多嵌段共聚物混合刷子。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，目标是创建稳定的周期结构。通过我们的合作，计算材料科学将被用于指导电刷的设计和选择，预测物理结构，并帮助检查这些新材料的物理性能。为了实现在这些刷层中实现均匀长程有序的目标，我们将结合导引结构来研究溶剂蒸气退火法和热瞬变激光尖峰退火法。将使用各种分析方法对刷子进行表征，包括X射线反射仪、掠入射(GI)SAXS和WAXS、中子反射率和风暴超分辨率荧光显微镜测量。将在新的棒-线圈混合电刷上进行电荷传输测量。每种技术都将提供有关材料内部或表面组织的信息，并有助于我们对所产生的结构的理解。

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.