(482a) Hierarchical Biopolymer Nanostructures for Active Microplastics Remediation and Sustainable Polymer Substitutes

The replacement of synthetic nanomaterials with biodegradable alternatives made from abundant and sustainable natural sources is a challenge of high societal importance. Our group reported earlier how lignin nanoparticles formed by antisolvent precipitation could serve as functional substitutes for silver nanoparticles in antimicrobials. Later, we discovered that the process of antisolvent precipitation under shear also enables the formation of diverse classes of biopolymer structures, including fibrillar nanomaterials. We will focus on the unique capabilities in environmental remediation and sustainable materials enabled by one such new material with hierarchical morphology called soft dendritic colloids (SDCs). The fractal branching and contact splitting phenomena enable SDCs gelation at very low volume fractions, strong adhesivity, and ability to form new types of nonwovens and reinforced biocomposites. One emerging application of the SDCs with potentially high societal impact is as cleaners that capture microplastics in lieu of traditional water remediation methods such as filtration and centrifugation. We use the unique properties of the SDCs in “active microcleaners,” which are made of chitosan and infused with a small amount of fatty acid, enabling them to self-propel and self-disperse in water. The rehydrated SDCs could enable the cleanup of microplastics in various types of aquifers, including saline seawater. Further, biopolymer SDCs can form hydrogels with synergistic colloidal and molecular networks. This opens the ability to engineer high-performance multifunctional composite films made of biopolymers: agarose matrix reinforced with chitosan SDCs. Owing to the entangled hierarchical SDCs network, the reinforced biocomposites have excellent mechanical performance, high optical transmittance, hydrostability, bactericidal activity and soil biodegradability. These results suggest a universal strategy for manufacturing of natural-source composite materials that could serve as substitutes for petroleum-based plastics.