Forming functional surfaces through surface-anchored macromolecular networks

North Carolina State University, Raleigh NC

Investigators

Abstract

NON-TECHNICAL SUMMARY The 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 SUMMARY The 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.