Vapor Deposition Polymerization of Porous Polymers

CBET-0828437Anthamatten智力功绩。微孔、介孔和大孔聚合物在组织工程、光伏、微电子、储氢和气体分离等领域都有很大的应用价值。多孔聚合物通常通过聚合诱导相分离(PIPS)、热诱导相分离(TIPS)或其他相转化技术来制备。这项研究与传统的溶液或熔融相方法不同。其目标是开发气相沉积聚合(VDP)作为一种可控的、对环境无害的技术来生产多孔和微结构聚合物。反应性单体和非反应性物种(致孔剂)将被共沉积到冷却的衬底上，以强制相分离并阻止动力学捕获的微米和纳米级微结构。这一概念将通过两个途径来研究：i)无定形聚合物的自由基链生长聚合和ii)刚性棒状高性能聚合物的缩聚。对于这两种情况，反应物和致孔剂浓度都将随着时间的推移而系统地变化，以产生与深度相关的形态和密度。这将使定制设计不对称薄膜的新途径成为可能。第二个目标是将观察到的形貌与工艺条件和相行为模型进行机械联系。为了实现这一点，将使用光学和电子显微镜技术对沉积的薄膜进行横截面分析。最初的实验主要集中在聚甲基丙烯酸甲酯作为一种体系来研究聚合物在致孔剂存在下的自由基生长。结果表明，薄膜可以从气相中以可控和可重复的方式生长。当引入低摩尔质量的致孔剂时，会发生相分离。为了研究缩聚反应，对第二个低压(~10-6Torr)VDP反应器进行了改造，以用于聚酰亚胺前体与可热降解致孔剂的共沉积。将进行类似的实验，使用p型酞菁染料(而不是致孔剂)来制造和测试聚合物稳定的光伏电池。更广泛的影响。这项研究与潜在的应用有很强的联系。具体地说，微孔刚性棒聚合物的VDP将为1)全有机气体分离膜和储氢材料，2)符合当前微电子加工趋势的低K介电材料，以及3)聚合物稳定的有机光伏提供新的途径。预计至少其中一个方向的未来研究计划将从这项研究中产生。研究还将有助于更好地理解微米厚聚合物薄膜中发生的本体聚合、相分离和玻璃化。这项研究最终将提高控制微米级膜特征及其一维空间分布的能力。研究和教育的结合将通过课程开发、实践应用项目和本科生和研究生课程的专题来实现。社区外展活动包括组织专业发展、绿色工程、为当地高中教师举办讲座。这些讲座将突出环境问题和解决方案，并提供新的教学工具，以弥合现实生活中的问题和传统教科书学习之间的差距。

CBET-0828437Anthamatten Intellectual Merit. Micro-, meso-, and macroporous polymers greatly benefit the fields of tissue engineering, photovoltaics, microelectronics, hydrogen storage, and gas separations. Porous polymers are often produced through polymerization-induced phase separation (PIPS), thermal-induced phase separation (TIPS), or other phase-inversion techniques. This study represents a departure from traditional solution- or melt-phase methods. The goal is to develop vapor deposition polymerization (VDP) as a controllable, environmentally sound technique to producing porous and micro-structured polymers. Reactive monomers and non-reactive species (porogens) will be co-deposited onto a cooled substrate to force phase separation and arrest kinetically trapped micro- and nano-scale microstructures. The concept will be studied via two avenues: i) radical chain-growth polymerization of amorphous polymers and ii) condensation polymerization of rigid-rod, high performance polymers. For both cases, reactant and porogen concentrations will be systematically varied with time to create depth-dependent morphologies and densities. This will enable new routes to custom-designing asymmetric membranes. A second goal is to mechanistically relate observed morphologies to process conditions and to models of phase behavior. To achieve this, cross-sectional analysis of as-deposited films will be studied using optical and electron microscopy techniques. Initial experiments have focused on poly(methyl methacrylate) as a system to study free-radical growth of polymers in the presence of a porogen. Results indicate that films can be grown from the vapor phase in a controlled and repeatable manner. When a low-molar mass porogen is introduced, phase separatio occurs. To study condensation polymerization, a second low pressure (~10-6 Torr) VDP reactor has been reconfigured for co-deposition of polyimide precursors with thermally-degradable porogens. Similar experiments will be conducted using p-type phthalocyanine dyes (instead of a porogen) to fabricate and test polymer-stabilized photovoltaics. Broader Impacts. The research has strong connections to potential applications. Specifically, VDP of microporous rigid-rod polymers will provide new routes to 1) all-organic gas separation membranes and hydrogen storage materials, 2) low-K dielectric materials that are compatible with current trends in microelectronics processing, and 3) to polymer-stabilized organic photovoltaics. It is expected that future research programs in at least one of these directions will spawn from this study. Research will also lead to an improved understanding of bulk polymerization, phase separation, and vitrification occurring in micron-thick polymer films. The study will ultimately improve the ability to control micron-scale membrane features and their one dimensional spatial distribution. The integration of research and education will be through curriculum development of hands-on application projects and special topics in undergraduate and graduate-level courses. Community outreach activities include organizing professional development, Green Engineering, lectures for local high school teachers. These lectures will highlight environmental issues and solutions, and provide new teaching tools to bridge the gap between real-life problems and traditional textbook learning.