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

由这笔赠款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，促进了科学和技术的发展，并影响了国家的繁荣。化学气相聚合是一种气相化学物质在表面反应生成薄聚合物膜的过程。尽管化学气相聚合已被工业广泛采用来产生聚合物涂层，例如用于微电子工业，但聚合物涂层仅限于平板薄膜。该奖项支持将化学气相聚合的能力扩展到大规模制造具有量身定做的纳米结构的表面涂层所需的基础研究，这些结构包括端接纳米纤维阵列或“纳米玻璃”、互连纳米纤维或“纳米片”的准二维网络，以及刚性端接纳米纤维或“纳米钉床”。这种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滤膜。这一合作项目为研究生在下一代制造工艺方面的多学科培训提供了突出的背景。该项目还整合了一项倡议，重点是让资深学生参与先进制造研究。这个项目背后的科学方法是基于两个基本上互不相连的领域--液晶和化学气相聚合--的思想汇聚。具体地说，表面负载的液晶薄膜被用作动态分子模板，通过化学气相聚合来指导聚合物纳米结构的形成。后者是通过对环芳烃的热升华和热解，然后聚合成形状可控的以液晶薄膜为模板的纳米结构来实现的。这项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，例如纳米纤维片，可以通过化学气相聚合大规模地获得液晶膜。利用含有分散微粒和不相容油滴的多相液晶膜，研究了拓扑缺陷在液晶模板化化学气相聚合中作用的基本问题。后合成工艺也被探索为实现纳米结构和功能特性的扩展调色板的方法，例如，通过后沉积热解制备的导电和形态可调的纳米纤维阵列的合成。这项研究的其他关键方面围绕着制造具有紧急光致发光、电学和传输特性的功能薄膜。该方法背后的一个统一的基本挑战是了解在原子级结构中编码的信息，例如，手性，在化学气相聚合过程中如何通过液晶在空间尺度上被液晶放大。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。

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.