Mixed Rod-Coil Polymer Brushes Tailored for Controlled Surface Topography

第1部分：非技术概述：聚合物是组成我们所使用的多种涂料、织物和塑料的长分子。有些聚合物可以是柔韧的、柔软的。其他聚合物可能又长又硬。通过将坚硬和柔软的聚合物结合在一个表面上形成的单一系统中，我们已经了解到，我们可以使用仔细的温度控制和涂层方法来制作纳米级的钉状刷状表面。PI和他的团队计划通过制造软和硬聚合物的新组合，通过使用先进的工具来研究它们的组织，并通过使用计算机对结构进行建模和预测它们的行为，来更好地了解这种表面形成过程。这种制作曲面的新方法开辟了许多有趣的应用领域。例如，表面模仿病毒表面上存在的蛋白质尖峰，自然界使用这些尖峰来识别目标细胞，参与进入细胞，并防止抗体识别。这些材料可以用来研究细胞的行为，主题从它们如何工作到免疫系统的行为。由于尖峰是垂直排列的，它们还可以充当纳米线，因此它们可以用于太阳能电池和电池等能源生产和存储系统。最后，这些尖峰可能是压电的，也就是说，它们可以将电能转化为运动(或声音)，将运动转化为电能。该研究项目还将作为一种机制，向学生传授聚合物和材料科学知识，培养具有全球意识的研究生，并让学生接触到合作环境。研究生将能够作为团队的一部分与我们的合作者的研究小组合作，并参与交流访问。从这些研究项目中学到的知识将被用于教授K-12学生，并应用于高中教师的研讨会。第二部分：技术概述：使用活性自由基聚合法合成的线团聚合物刷将与从使用各种活性和伪活性化学物质制成的表面生长的具有高持续长度的棒状刷子结合在一起。在溶剂处理辅助下的相分离和纳米光刻指导下的相分离将被用来控制平面结构。各种化学和加工方法将被用来限制宏观相分离，从而直接组装地形和化学结构。电刷生长将采用新的、化学上量身定做的电刷引发剂，用于单链和二元链的生长，以形成棒-卷混合电刷对。为了指导电刷结构和棒-线圈相分离，将使用最先进的光刻方法控制电刷尖峰的间距，在几十纳米的长度尺度上对电刷引发剂进行图案化。刷子的组织将与计算预测进行比较，计算预测将用于指导刷子的设计和选择，并预测结果的物理结构和辅助表征研究。刷子的表征将使用一系列分析方法，包括掠入射(GI)SAXS和WAXS、中子反射率和共振软X射线散射(RSoXS)测量。研究棒-线圈电刷薄膜的导电性和压电性将有助于我们理解混合电刷的结构。通过合作，对这些材料作为细胞膜衬底、靶向生物分子结合、作为压电材料和作为具有不寻常传输路径的导电材料的研究，也将提供关于关键长度尺度和杆刷组织的信息。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY: Polymers are long molecules that make up the many kinds of coatings, fabrics and plastics we use. Some polymers can be flexible and soft. Other polymers can be long and stiff. By combining stiff and flexible polymers in a single system formed on a surface, we have learned that we can make nanoscale spiky brush-like surfaces using careful temperature control and coating methods. The PI and his group plan to better understand this surface formation process by making new combinations of soft and stiff polymers, by using advanced tools to study their organization, and by employing computers to model the structure and to predict their behavior. This new way of making surfaces opens up many interesting applications. For example, the surface mimics the protein spikes present on virus surfaces that are used by nature to identify target cells, take part in the entry into the cell, and also to prevent identification by antibodies. These materials can be used to study the behavior of cells on topics ranging from how they work to the behavior of the immune system. Because the spikes are vertically aligned, they may also act as nanowires, so they can be used in energy production and storage systems like solar cells and batteries. Finally, these spikes may be piezoelectric, i.e. they could convert electrical energy to motion (or sound) and motion to electrical energy. This research program will also serve as a mechanism to teach students about polymers and materials science, create globally aware graduate students, and expose students to a collaborative environment. Graduate students will be able to work with the research groups of our collaborators as parts of teams and to take part in exchange visits. Lessons learned from these research programs will be used to teach K-12 students and to be applied in high school teachers' workshops. PART 2: TECHNICAL SUMMARY:Coil polymer brushes synthesized using living radical polymerization methods will be combined with rod brushes with high persistence lengths grown from surfaces made using a variety of living and pseudo-living chemistries. Phase separation aided by solvent processing and guided by nanolithography will be used to control in-plane structure. A variety of chemical and process methods will be used to limit macroscopic phase separation and thereby direct assembly of topographical and chemical structures. Brush growth will employ new, chemically tailored brush initiators for single chain and binary chain growth to form rod-coil mixed brush pairings. To direct brush structure and rod-coil phase separation, brush initiators will be patterned at length scales of a few 10s of nanometers using state-of-the-art lithography methods to control spacing of the brush spikes. Brush organization will be compared to computational predictions which will be used to guide both brush design and selection and to anticipate the resulting physical structure and aid characterization studies. Characterization of the brushes will be made using a selection of analytical methods including grazing incidence (GI) SAXS and WAXS, neutron reflectivity and resonant soft X-ray scattering (RSoXS) measurements. Studies of the conductivity and piezoelectric character of the rod-coil brush films will aid in our understanding of the mixed brush structure. Through collaborations, studies of these materials as cell membrane substrates, for targeted biomolecular binding, as piezoelectric and as conducting materials with unusual transport pathways, will also provide information about key length scales and rod-brush organization. .This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.