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Aromatic Zipper Topology Dictates Water-Responsive Actuation in Phenylalanine-Based Crystals |
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| Authors: | Fahmeed K Sheehan Haozhen Wang Darjan Podbevšek Elma Naranjo Janel Rivera-Cancel Cooper Moran Rein V Ulijn Xi Chen |
| Affiliation: | 1. Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, NY, 10031 USA
Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 5th Ave, New York, NY, 10016 USA Department of Chemistry, Hunter College, 695 Park Ave, New York, NY, 10065 USA;2. Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, NY, 10031 USA Ph.D. Program in Physics, The Graduate Center of the City University of New York, 365 5th Ave, New York, NY, 10016 USA;3. Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, NY, 10031 USA;4. Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, NY, 10031 USA Department of Chemical Engineering, The City College of New York, 275 Convent Ave, New York, NY, 10031 USA;5. Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, NY, 10031 USA Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 5th Ave, New York, NY, 10016 USA;6. Department of Chemistry, Hunter College, 695 Park Ave, New York, NY, 10065 USA |
| Abstract: | Water-responsive (WR) materials that reversibly deform in response to relative humidity (RH) changes are gaining increasing interest for their potential in energy harvesting and soft robotics applications. Despite progress, there are significant gaps in the understanding of how supramolecular structure underpins the reconfiguration and performance of WR materials. Here, three crystals are compared based on the amino acid phenylalanine (F) that contain water channels and F packing domains that are either layered (F), continuously connected (phenylalanyl-phenylalanine, FF), or isolated (histidyl-tyrosyl-phenylalanine, HYF). Hydration-induced reconfiguration is analyzed through changes in hydrogen-bond interactions and aromatic zipper topology. F crystals show the greatest WR deformation (WR energy density of 19.8 MJ m−3) followed by HYF (6.5 MJ m−3), while FF exhibits no observable response. The difference in water-responsiveness strongly correlates to the deformability of aromatic regions, with FF crystals being too stiff to deform, whereas HYF is too soft to efficiently transfer water tension to external loads. These findings reveal aromatic topology design rules for WR crystals and provide insight into general mechanisms of high-performance WR actuation. Moreover, the best-performing crystal, F emerges as an efficient WR material for applications at scale and low cost. |
| Keywords: | aromatic zippers peptide crystals stiffness water-responsive materials |