Hierarchically reinforced biopolymer composite films as multifunctional plastics substitute

The replacement of synthetic plastics with biodegradable alternatives made from abundant and sustainable raw materials is a challenge of high societal importance. We report a class of high-performance multifunctional composite films made of nano- and microscale reinforced naturally sourced biopolymers. These films are made of an agarose matrix reinforced with hierarchically branched soft dendritic colloids (SDCs) from chitosan. Owing to the highly entangled hierarchical network of the SDC nanofibrils, the reinforced composite has excellent performance with more than 4× higher toughness than non-reinforced agarose, high visible light transmittance, improved hydrostability, and remarkable bactericidal activity. Thus, these reinforced biopolymer composites could match or exceed the excellent mechanical, barrier, and optical properties of common synthetic polymer films. We also demonstrate the soil biodegradability of this composite material in a controlled environment. The results suggest a universal strategy for manufacturing natural-source composite materials that could serve as substitutes for petroleum-based plastics.