Janus Brushblock Copolymer Phase Behavior: Morphology and Thermodynamics

第一部分：非技术总结在纳米尺度(人类头发宽度的1/10000)形成精确和可定制结构的特种聚合物为开发用于选择性水和气体净化的有用多孔膜提供了一条途径，以及为以更小的组件构图更快的计算机微处理器提供了模板。这项研究计划将在化学、化学工程和材料科学之间的跨学科研究小组内，培训下一代科学家和工程师指导此类聚合物的设计和开发。通过结合先进的聚合物合成、纳米级的详细结构表征和由此产生的聚合物性质的表征，该项目将揭示非线性聚合物的新的分子设计规则，这些规则将导致它们在15纳米以下的长度尺度上自发自组织。这些研究将为美国工业提供技术知识，使其能够开发出保持全球竞争力的创新产品。与该项目相关的教育推广活动将侧重于开发简单、具有视觉吸引力的演示，其特点是将宏观材料自发地组织成肉眼可见的结构。这些演示将为K-12和大学水平的学生以及普通公众提供教育和兴奋的机会，了解基于聚合物的先进技术。第2部分：技术总结由于将两个或多个不相容的聚合物链段耦合到一个大分子中而导致的分子受挫，嵌段聚合物自组装成各种纳米结构的形态。微妙的热力学平衡决定了AB双嵌段聚合物微相分离时的最低聚合度(N)，这决定了可以形成的最小微域尺寸。一个潜在的嵌段聚合物应用依赖于它们的周期性微域作为先进的微电子和介孔无机材料的模板，具有低于15 nm的特征。减小双嵌段聚合物结构域尺寸的一种常见方法是减少N，同时增加A和B链段的化学不相容性。然而，这些新材料的应用往往需要昂贵的新材料加工方案的开发。本项目研究了Janus BottleBrush聚合物的微相分离行为，这是一种由线性AB双嵌段通过其连接点共价连接而成的非线性聚合物结构，作为驱动AB双嵌段以比其线性同系物更小的长度自组装的新手段。结合小角X射线散射、透射电子显微镜和流变学测量，将研究Janus瓶刷的相行为作为其组成、均聚物臂之间的化学不相容以及沿主干的刷毛接枝密度的函数。

Part I: NON-TECHNICAL SUMMARYSpecialty polymers that form precise and tailorable structures at the nanometer length scale (1/10000th of the width of a human hair) provide a route for developing useful porous membranes for selective water and gas purifications, as well as templates for patterning faster computer microprocessors with ever smaller components. This research program will educate the next generation of scientists and engineers in the guided design and development of such polymers, within an interdisciplinary research group situated at the interface between chemistry, chemical engineering, and materials science. Through combination of advanced polymer synthesis, detailed structural characterization at the nanoscale, and characterization of the resulting polymer properties, this project will reveal new molecular design rules for nonlinear polymers that lead to their spontaneous self-organization at length scales below 15 nanometers. These studies will provide American industry with technological knowledge that enables the development of innovative products that maintain global competitiveness. The educational outreach activities associated with this project will focus on the development of simple, visually attractive demonstrations featuring spontaneous self-organization of macroscopic materials into structures visible to the naked eye. These demonstrations will furnish opportunities for educating and exciting students at the K-12 and college levels, as well as the general public, about advanced technologies based on polymers. Part 2: TECHNICAL SUMMARYBlock polymers self-assemble into a variety of nanostructured morphologies, as a consequence of the molecular frustration induced by coupling two or more immiscible polymer segments into a single macromolecule. A delicate thermodynamic balance governs the lowest degree of polymerization (N) at which an AB diblock polymer microphase separates, which then dictates the smallest microdomain size that can form. One potential block polymer application relies on their periodic microdomains as templates for advanced microelectronics and mesoporous inorganic materials with sub-15 nm features. A common approach to reducing diblock polymer domain sizes is to decrease N, while increasing the chemical incompatibility of the A and B segments. However, applications of these new materials often require costly development of new materials processing protocols. This project investigates the microphase separation behavior of Janus bottlebrush polymers, a nonlinear polymer architecture derived from covalently linking linear AB diblocks through their junctions, as a new means for driving AB diblocks to self-assemble at smaller length scales than their linear homologs. Using a combination of small-angle X-ray scattering, transmission electron microscopy, and rheological measurements, the phase behaviors of Janus bottlebrushes will be studied as a function of their compositions, the chemical incompatibility between the homopolymer arms, and the graft density of the bristles along the backbone.