Forming functional surfaces through surface-anchored macromolecular networks

设计和制造具有功能性和可定制表面性能的材料是当前材料研究面临的最重要挑战之一。识别一种能够独立控制化学成分、表面形貌、官能团迁移率、机械性能和电荷的材料是一项艰巨的任务。由大分子组成的聚合物涂层通过附着在表面上的所谓交联点在不同位置连接起来，可能符合要求。阻碍这类材料广泛应用的一个主要障碍是需要化学合成特殊聚合物。该项目克服了这一限制，通过使用一系列简单的交联剂分子，将各种聚合物转化为表面锚定的交联聚合物涂层，这些交联剂分子要么是市售的，要么是非常容易合成的。因此，任何人都可以利用所提出的方法与各种起始材料相结合来制造具有可控成分、柔软度、表面形貌和其他重要物理化学特性的功能表面。导致这种表面形成的过程被设计为具有高度可扩展性，因此它们原则上可以应用于大面积表面。该研究项目也将有助于高中、本科生和研究生的理工科教育。这些包括科学培训和交流、演讲技巧以及科学和技术的伦理原则。外展活动将在当地场地（研究三角地区的高中和大学）以及弗吉尼亚州阿拉拉特的小学（位于我国最偏远的地区之一）举行。当地的K-12学生和教师将被鼓励参加研究/教育活动，通过个人指导和通过北卡州立大学的科学之家组织的计划。包括为研究三角地区的学术界、工业界和公众组织科学和外展会议的当前努力和未来计划。技术概述：该项目的中心目标是通过将具有高度可定制特性的聚合物网络薄膜附着在固体基材上来创建功能表面。这些聚合物网络由长链分子（即大分子）阵列组成，在几个节点（即交联点）上相互连接。聚合物网络是通过使用带有两个官能团A和B的小功能分子（SFMs）交联大分子而产生的，其中A与相邻的聚合物链形成化学键，而来自两个相邻的SFMs（或/和底物）的B基团形成化学或物理键，这取决于B单元的性质。这种方法使任何聚合物，无论其功能如何，都可以在表面上进行化学交联和固定。重要的是，SFMs要么是商业上可用的，要么可以很容易地合成。直接的科学和技术影响在于提供一个源不可知的框架来设计和生产具有受控化学成分、可调谐（和可擦除）拓扑结构、可定制的柔软度和摩擦以及其他相关的物理化学界面特征的表面。网络形成过程的简单性和可调性使其成为不需要高化学专业知识的科学家和工程师的理想选择，并将其范围扩大到生物医学和医疗保健科学，安全或国防。项目描述概述了旨在测试提出的网络生成假设和建立结构-过程属性的任务。具体而言，将建立一系列不同的SFMs，不同的退火时间和退火温度下网络形成的结构和动力学。通过将具有磁响应的纳米颗粒加入到SFMs中，可以产生功能聚合物网络涂层，该涂层可以根据外部磁场改变形貌的机械性能。该提案还概述了形成以水凝胶（即在水中膨胀的聚合物网络）和有机硅弹性体（即不需要溶剂保持柔韧性的柔性橡胶）为特征的双层结构的新方法。这些层压板经常用于生物医学，形状变化和可变形材料，但它们的制备目前依赖于弹性体组件的苛刻物理处理。所提出的方法消除了这一限制，使这些重要复合材料的制造新颖、清洁和可重复。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。

NON-TECHNICAL SUMMARYThe design and fabrication of materials with functional and tailorable surface properties represents one of the most important challenges facing current materials research. It is daunting to identify a material that enables independent control of chemical composition, surface topography, mobility of functional groups, mechanical properties, and charge. Polymer coatings comprising macromolecules linked at various locations via so-called crosslink points attached to surfaces may fit the bill. A major obstacle that has hindered widespread application of such materials is the need for chemical synthesis of specialty polymers. This project overcomes this limitation by turning a wide variety of polymers into surface-anchored crosslinked polymer coatings using a family of simple crosslinker molecules that are either commercially available or are very easy to synthesize. Thus, anyone can utilize the proposed method in combination with a variety of starting materials to fabricate functional surfaces with controlled composition, softness, surface topography, and other important physico-chemical characteristics. The processes leading to the formation of such surfaces have been designed to be highly scalable, so that they could be, in principle, applied to coat large-area surfaces. This research project will also contribute to education of high school, undergraduate, and graduate students in science and engineering. These involve scientific training and communication, presentation skills, as well as ethical principles in science and technology. Outreach activities in both local venues (high schools and colleges in the Research Triangle area) as well as at elementary school in Ararat, VA (located in one of the most rural areas of our country) will take place. Local K-12 students and teachers will be encouraged to participate in the research/educational activities through individual mentoring and via programs organized by NC State's Science House. Current efforts and future plans for organizing scientific and outreach meetings for academe, industry, and general public in the Research Triangle region are included.TECHNICAL SUMMARYThe central goal of this project is to create functional surfaces by attaching polymer network films with highly tailorable characteristics onto solid substrates. These polymer networks comprise arrays of long chain molecules (i.e., macromolecules) connected mutually at several nodes (i.e., crosslink points). The polymer networks are generated by crosslinking macromolecules using small functional molecules (SFMs) equipped with two functional groups, A and B, wherein A forms a chemical bond with a neighboring polymer chain, and B groups from two neighboring SFMs (or/and the substrate) form either a chemical or a physical bond, depending on the nature of the B units. This method makes any polymer, regardless of its functionality, amenable to chemical crosslinking and immobilization on surfaces. Importantly, the SFMs are either available commercially or can be readily synthesized. The immediate scientific and technological impact lies in providing a source-agnostic framework to design and produce surfaces with controlled chemical composition, tuned (and erasable) topology, tailorable softness and friction, and other relevant physico-chemical interfacial characteristics. The simplicity and tunablity of the network-forming process makes it ideal for scientists and engineers without requiring high chemical expertise, and broadens its scope to biomedical and healthcare sciences, security, or national defense. The project description outlines tasks that aim at testing the proposed hypothesis of network generation and establishing structure-process properties. Specifically, the structure and kinetics of network formation will be established for a series of different SFMs, different annealing times, and annealing temperatures. Functional polymer network coatings that alter mechanical properties of topography in response to external magnetic fields will be generated by incorporating magnetically-responsive nanoparticles into the SFMs. The proposed effort also outlines new ways of forming bilayers featuring hydrogels (i.e., polymer networks that swell in water) and silicone elastomers (i.e., flexible rubbers that do not require solvent to remain flexible). These laminates are frequently used in biomedical, shape-changing, and deformable materials, yet their preparation currently relies on harsh physical treatment of the elastomer component. The proposed methodology removes this limitation and enables novel, cleaner, and reproducible manufacturing of these important composite materials.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.