Multilayered Protective Biomimetic Coatings from Sustainable Chitin and Chitosan
Abstract
Chitin and chitosan are bio-derived polymers that have demonstrated large potential in numerous technological sectors involving applications in medical, industrial and biotechnological arenas. However, their replacement potential for application areas dominated by petroleum-derived engineering plastics remains challenging due to their inferior mechanical and other engineering properties. To this end, this proposal will develop biomimetic, tough and durable multilayer films wherein each layer has a specific function, to form multifunctional apparel protective coatings for DoD needs. As a result, the flexible fabric coatings will have multifunctional properties for impact resistance to projectiles or laser, while simultaneously absorbing toxic gas, and exhibiting antimicrobial properties. The materials used are largely biodegradable in nature, derived from sustainable chitin and chitosan obtained via green processing pathways. Chitin, a derivative of glucose, and abundantly available as the primary component of cell walls in fungi and exoskeletons of arthropods such as crustaceans, insects, molluscs, and fish scales, is a brittle material. By contrast, chitosan-based materials can be soft and flexible, yet are typically derived through treating chitin with strong base, which is environmentally unfriendly. This proposal will use green enzymatic routes to convert chitin to a family of chitosan-based polysaccharides with diverse functional moieties, useful for toughening of nanostructured architectural film layers of the coatings. Multifunctional coating properties will be accomplished by hierarchical multilayering with a quad layer structure, with each layer uniquely optimized for a specific functional property. Gradient coatings found in nature, such as the skins of fruits and vegetables, have impervious and impact resistant antimicrobial outer layers that trap moisture inside, and slowly transition to softer interiors. Our analogously designed biomimetic hierarchical quad multilayer will comprise the following structure, from the exterior to interior: 1) Impact Resistant Layer: Hardened, ballmilled, densely-packed chitin nanofiber outer layer, grafted with inter-particle entangling polymer or functionally cross-linkable biopolymer matrix. Such dense polymer-grafted nanofibers (PGNFs) have been shown recently to greatly enhance mechanical toughness. 2) Energy Absorbing Crush Layer: Sub-layer of porous structures for impact resistance, analogous to that found in sublayer in skins of fruits such as oranges and similar to the crumple zones in automobiles. This layer will be comprised of a collapsible 3D-printed strut structure for shock and energy dissipation. 3) Toxic Gas Absorbing Layer: High surface area activated charcoal nanoparticles dispersed in chitosan with high gas sorption capacity. Light cross-linking of the chitosan with functional groups will prevent swelling-induced failure of this layer. 4) Textile Adhesion Layer: An adhesion promoting layer for robust binding of the coating to canvas and other textiles. Numerous techniques will be used to characterize the microstructure of the individual layers as well as of the final composite coatings, including advanced surface probe microscopy, spectroscopy, and X-ray and neutron scattering. Structural parameters will be correlated to a battery of physical properties including high-speed nanoprojectile impact, nanoindentation, tensile properties, delamination / adhesion, gas sorption and gas barrier properties, and antimicrobial properties for optimization of structure-property relationships.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 31, 2020
- Source ID
- W911NF2010281
Entities
People
- Alamgir Karim
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- University of Houston