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

这项拨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，推动了科学技术的发展，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上反应形成聚合物薄膜的过程。尽管化学气相聚合已被工业广泛采用来制造聚合物涂层，例如用于微电子工业，但聚合物涂层仅限于平面薄膜。该奖项支持基础研究，以扩大化学气相聚合的能力，大规模制造具有定制纳米结构的表面涂层，包括末端附着的纳米纤维阵列或“纳米草”，相互连接的纳米纤维或“纳米片”的准二维网络，以及刚性末端附着的纳米纤维或“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。该合作项目为下一代制造工艺研究生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旨在让资深学生参与先进制造研究的倡议。这个项目背后的科学方法是基于两个基本不相关的领域——液晶和化学蒸汽聚合——的思想的融合。具体来说，支持在表面上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。后一过程是通过热升华和热解副环环烷来实现的，随后聚合成由液晶膜模板化的形状控制纳米结构。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，例如纳米纤维片，可以通过化学气相聚合成液晶膜进行大规模获取。利用含有微粒子分散体和不混相油滴的多相液晶膜，研究了拓扑缺陷在液晶模板化学气相聚合中的作用。合成后工艺也被探索作为一种实现纳米结构和功能特性的扩展调色板的方法，例如，通过沉积后热解制备的导电和形态可调纳米纤维阵列的合成。研究的其他关键方面围绕着具有新兴光致发光，电学和输运特性的功能薄膜的制造。该方法的一个统一的基本挑战是理解在化学蒸汽聚合过程中，反应性单体的原子尺度结构中编码的信息（例如手性）是如何被液晶在空间尺度上放大的。该奖项反映了美国国家科学基金会的法定使命，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.