Hierarchical Cellulose Nanocrystal Blends for Bioinspired Damage Tolerant Photonic Films
Bharath NMN Natarajan, Ajay Krishnamurthy, Caglar Dogu Emiroglu, Amanda L. Forster, E. J. Foster, Christoph Weder, Douglas M. Fox, Jan Obrzut, Jeffrey W. Gilman
Attempts to emulate strong and tough natural composites using wood cellulose nanocrystals (CNCs) fall short in mechanical performance due to the low shear transfer ability of CNC interfaces in their helicoidal ensembles. This shortcoming is ascribed to the small CNC-CNC overlap lengths that minimize the cumulative interaction strengths. Herein, we present a simple green strategy to fabricate superior helicoidal CNC films with properties that rival those of the best natural materials. Assembling the wood CNCs with a minority fraction of large aspect ratio tunicate derived CNCs (t-CNCs), we report remarkable synergistic enhancements in modulus, strength, ductility and toughness. The mechanical properties reported here are some of the best reported for helicoidal CNC materials thus far. At t-CNC contents greater than 5 % by mass the blended films also display UV reflecting behavior. We identify these films as excellent starting materials or scaffolds for biomimetic nanocomposite fabrication. As is, these damage tolerant optically active materials hold potential for application as protective coatings in the automobile, aerospace, electronics and infrastructure industries.