Forming functional surfaces through surface-anchored macromolecular networks

非技术总结设计和制造具有功能和可裁剪表面特性的材料是当前材料研究面临的最重要的挑战之一。要找到一种能够独立控制化学成分、表面形貌、官能团的流动性、机械性能和电荷的材料是令人望而生畏的。聚合物涂层包括通过连接到表面的所谓交联点在不同位置连接的大分子，可能符合这一要求。阻碍这类材料广泛应用的一个主要障碍是需要特殊聚合物的化学合成。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变为表面锚定的交联型聚合物涂层，这些分子要么是商业上可以获得的，要么非常容易合成。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工艺被设计成高度可伸缩的，因此它们原则上可以应用于大面积表面的涂层。这项研究项目还将对高中、本科生和研究生的科学和工程教育做出贡献。其中包括科学培训和交流、演讲技巧以及科学和技术方面的伦理原则。将在当地场所(研究三角地区的中学和大学)以及弗吉尼亚州阿拉拉特的小学(位于我国最农村的地区之一)开展外联活动。通过个人辅导和北卡罗来纳州立大学科学之家组织的计划，将鼓励当地的K-12学生和教师参与研究/教育活动。该项目的中心目标是通过将具有高度可裁剪特性的聚合物网络薄膜附着在固体基板上来创建功能表面。这些聚合物网络包括在几个节点(即交联点)相互连接的长链分子(即大分子)的阵列。聚合物网络是通过使用配备有两个官能团A和B的小功能分子(SFMS)使大分子交联而产生的，其中A与相邻的聚合物链形成化学键，而来自两个相邻SFMS(或/和底物)的B基团形成化学键或物理键，这取决于B单元的性质。这种方法使任何聚合物，无论其官能度如何，都可以在表面进行化学交联和固定化。重要的是，SFMS既可以在商业上获得，也可以很容易地合成。直接的科学和技术影响在于提供了一个与来源无关的框架，以设计和制造具有可控化学成分、可调(和可擦除)拓扑、可定制的柔软性和摩擦力以及其他相关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科学家和工程师的理想选择，无需很高的化学专业知识，并将其范围扩大到生物医学和保健科学、安全或国防。项目描述概述了旨在测试所提出的网络生成假说和建立结构-过程属性的任务。具体地说，将建立一系列不同的SFM、不同的热处理时间和热处理温度下的网络形成的结构和动力学。功能聚合物网络涂层将通过在SFMS中加入磁性响应性纳米颗粒来产生，该涂层可以响应外部磁场而改变表面的机械性能。拟议的工作还概述了形成具有水凝胶(即在水中膨胀的聚合物网络)和硅橡胶(即不需要溶剂保持柔性的柔性橡胶)的双层的新方法。这些层压板经常用于生物医学、形状变化和可变形材料，但目前它们的制备依赖于对弹性体部件的苛刻物理处理。拟议的方法消除了这一限制，使这些重要复合材料的制造变得新颖、清洁和可再生。该奖项反映了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。

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.