Engineering Photomechanical Crystals and Composites with Ultrahigh Work Densities
Abstract
Approved for Public ReleasePhotoreactive molecular crystals provide a unique combination of high elastic modulus and high strain, leading to predicted photomechanical work densities up to 10^8 J/m^3. These values represent a factor of 100-1000 improvement over standard actuator materials like polymers or ceramics. Organization of molecular nanocrystals within a supporting polymer matrix provides a general strategy for scaling their favorable photomechanical properties up to the device level. Such molecular crystal-polymer template composites have exhibited a record-breaking work density of 5×10^4 J/m^3 by leveraging the concepts of mechanical impedance matching and epitaxial growth. To realize the full potential of photomechanical molecular crystals, the proposed research will coordinate the efforts of four PIs with an established track record of collaboration. Bardeen is an expert in molecular crystal spectroscopy and photochemistry. Beran has developed computational tools for the prediction of molecular crystal structure and properties. Read de Alaniz is a synthetic organic chemist who specializes in photoresponsive molecules and polymers. Hayward is a chemicalengineer and materials scientist with extensive experience in responsive polymers and composites. Together, they will undertake two parallel and interconnected efforts. Effort 1 centers on optimizing the molecular crystal engine through a combination of quantumchemical computations, synthesis, and crystal characterization. Beran and Read de Alaniz will identify suitable molecular targets,whose crystal packing and potential for work generation will be evaluated by Beran#s computations. Read de Alaniz will then synthesize the most promising candidates, whose spectroscopic properties, photochemical reactivity, and work output at the crystal level will be evaluated by Bardeen and Hayward. Effort 2 addresses the problem of how to assemble the photomechanical crystals into practical materials. Hayward will optimize the filling of engineered polymer templates via solvent or melt growth, relying on lattice matching and shape-guided growth to passively control crystal alignment. Hayward and Bardeen will develop new approaches based on active ordering of nanocrystals in a polymer matrix using external fields and controlled crystal growth. The photomechanical performance of both types of crystal-polymer composites will be characterized in detail. Composite design will rely on guidance from Effort 1to identify crystals with properties like surface charge density and anisotropic electromagnetic susceptibilities that can be exploited for ordering and control of growth kinetics. Results from Effort 2 will help refine the molecular design of Effort 1 toward molecules that can be more easily processed into useful composites. The coordinated research effort will result in two major outcomes. First, it will generate a well-characterized library of photomechanical molecules and crystalsthat will provide the foundation forfuture optimization efforts, including those based on machine learning. Second, the combination of mechanically active crystals with a matched polymer host will give rise to a new class of photon-powered composites with work densities on the order of 10^7 J/m^3. These composites will retain the processability and scalablity advantages of polymers while simultaneously benefiting from the high energy density of molecular crystals. When combined with optical fiber or free-space light delivery systems, they will provide new capabilities for the design of mechanical actuator structures.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 08, 2024
- Source ID
- N000142412358
Entities
People
- Christopher J Bardeen
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents