Collaborative Research: Liquid Crystal-Templated Chemical Vapor Polymerization of Complex Nanofiber Networks

该资助支持的研究产生了开发新型聚合物薄膜新制造工艺所需的基础知识，推动了科学技术的发展，并影响了国家的繁荣。化学气相聚合是气相化学物质在表面上反应以产生薄聚合物膜的过程。尽管化学气相聚合已被工业广泛采用来产生聚合物涂层，例如，对于微电子工业，聚合物涂层被限制为平膜。该奖项支持将化学气相聚合的能力扩展到具有定制纳米结构的表面涂层的大规模制造所需的基础研究，包括末端连接的纳米阵列或“纳米草”，互连纳米纤维或“纳米片”的准二维网络，以及刚性末端连接的纳米纤维或“纳米钉床”。下一代纳米结构涂层的潜在应用包括改进的粘合剂、生物医学传感器、用于生长替代器官的生物材料和水过滤膜。这个合作项目为研究生在下一代制造过程中的多学科培训提供了一个出色的背景。该项目还整合了一项举措，重点是让资深学生参与先进制造研究。该项目的科学方法基于两个基本上不相关的领域-液晶和化学气相聚合的思想融合。具体而言，支撑在表面上的液晶薄膜被用作动态分子模板，以引导通过化学气相聚合形成聚合物纳米结构。后一个过程是通过对环芳的热升华和热解来实现的，其随后通过液晶膜模板化成形状受控的纳米结构。该研究阐明了控制新发现的聚合物形态形成的化学和物理过程，例如，可通过化学气相聚合成液晶膜来大规模访问的液晶片。通过使用含有微粒和不混溶油滴的分散体的多相液晶膜，研究了关于拓扑缺陷在液晶模板化学气相聚合中的作用的基本问题。还探索了合成后工艺作为实现扩大纳米结构和功能特性的方法，例如，通过沉积后热解制备的导电和形态可调的纳米阵列的合成。研究的其他关键方面围绕着制造具有光致发光，电气和传输特性的功能薄膜。该方法的一个统一的基本挑战是理解原子尺度结构中编码的信息，例如，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Research supported by this grant generates foundational knowledge needed to develop new manufacturing processes for novel polymer films, advancing both science and technology and impacting national prosperity. Chemical vapor polymerization is a process where gas phase chemical species are reacted on surfaces to create thin polymer films. Although chemical vapor polymerization has been widely adopted by industry to create polymer coatings, e.g., for the microelectronics industry, the polymer coatings have been limited to flat films. This award supports fundamental research needed to expand the capabilities of chemical vapor polymerization to large-scale manufacturing of surface coatings with tailored nanoscopic structures, including end-attached nanofiber arrays or “nanograsses”, quasi-two-dimensional networks of interconnected nanofibers or “nanosheets”, and rigid end-attached nanofibers or “bed-of-nanonails”. Potential applications for this next generation of nanostructured coatings include improved adhesives, biomedical sensors, biomaterials for growing replacement organs, and water filtration membranes. This collaborative project provides an outstanding context for the multidisciplinary training of graduate students in next-generation manufacturing processes. The project also integrates an initiative that is focused on the engagement of veteran students in advanced manufacturing research. The scientific approach underlying this project is based on a convergence of ideas from two largely disconnected fields – liquid crystals and chemical vapor polymerization. Specifically, thin films of liquid crystals supported on surfaces are used as dynamic molecular templates to guide the formation of polymeric nanostructures via chemical vapor polymerization. The latter process is achieved by thermal sublimation and pyrolysis of paracyclophanes, which subsequently polymerize into shape-controlled nanostructures templated by the liquid crystal films. The research elucidates the chemical and physical processes that control the formation of newly discovered polymeric morphologies, e.g., nanofiber sheets, that can be accessed at scale by chemical vapor polymerization into liquid crystal films. Fundamental questions regarding the role of topological defects in liquid crystal-templated chemical vapor polymerization are investigated by using multiphase liquid crystal films containing dispersions of microparticles and immiscible oil droplets. Post-synthesis processes are also explored as an approach to achieving an expanded palette of nanostructures and functional properties, e.g., the synthesis of electrically conductive and morphologically tunable nanofiber arrays prepared via post-deposition pyrolysis. Other key aspects of the research revolve around the manufacturing of functional thin films with emergent photoluminescent, electrical, and transport properties. A unifying fundamental challenge underlying the approach is understanding how the information encoded in the atomic-scale structure, e.g., chirality, of reactive monomers is amplified across spatial scales by the liquid crystal during chemical vapor polymerization.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.