Controlling silicone polyHIPE materials properties with triblock copolymer surfactants: A route to bottom-up synthesis of metamaterials

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

NON-TECHNICAL SUMMARY: Metamaterials are human-made materials that possess extraordinary physical properties and have been proposed for use as sound barriers, creating super-lenses of remarkable resolution, making invisibility cloaks, and other emerging areas. The objective of this research is to generate new, tailorable, metamaterials in ways that can be easily scaled up and do not rely on complex and expensive approaches. Specifically, this work will produce porous polysilicone materials and generate fundamental understanding of how the structure of polymers used to prepare the porous materials can control their performance as soft metamaterials. In addition to the expected positive impact on metamaterials research, the findings from this work will also benefit scientists studying porous materials used for biomedical and regenerative medicine applications and new silicone materials. There is also a great need for a diverse, globally engaged U.S. workforce possessing world-class skills. This workforce is expected to enhance U.S. leadership in research and education and strengthen national economic competitiveness. The activities in this proposal will include international collaborative research opportunities between the University of Cincinnati and the University of Bordeaux. This will include a trip to France for two undergraduate students from the University of Cincinnati to participate in hands-on research experiences with experts on metamaterials. The effectiveness of the international experiences will be evaluated each year and the results disseminated though conference presentations and scientific papers. TECHNICAL SUMMARY: The fabrication of metamaterials is largely achieved by top-down lithography approaches, which are difficult to scale-up. Alternatively, a bottom-up strategy to make optical and acoustic metamaterials is possible using silicone polymerized high-internal-phase emulsions (polyHIPEs). The objective of this research is to generate new, tailorable, metamaterials. The central hypothesis tested in this project is that the structure and functionality of block copolymer surfactants control the stability and properties of water-in-silicone emulsions and thus the resulting polyHIPEs, and hence the final metamaterials properties. The central hypothesis will be tested by pursuing the following specific aims: Aim 1: Determine how the porosity, storage moduli, and damping of silicone polyHIPEs control the speed of sound within the material as a result of the structure of water-in-silicone emulsions. Aim 2: Prepare polymer cross-linkers as surfactants for water-in-silicone emulsions to maintain porosity and compressibility of silicone polyHIPEs and stabilize gold nanoparticles within the polyHIPE. Accomplishment of these Aims is expected to establish how amphiphilic block polymer surfactant chemistry can be used to prepare new porous silicone polyHIPE materials. This is timely and important, as it could afford tunable, simple, and relatively cheap acoustic metamaterials for applications in imaging, cloaking, and long-wavelength noise reduction. The graduate and undergraduate students engaged in this research will be trained in polymer chemistry, materials synthesis and characterization, and will participate in international collaborative research. . 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.