Strong and tough bioplastics prepared by in-situ polymerization of ε-caprolactone-oligomers in lignocellulosic nanofiber network

Cellulose biocomposites have emerged as attractive alternatives to fossil-based plastics because of their excellent renewability and biodegradability; however, their water resistance and mechanical properties remain challenging. Herein, a cellulose- containing bioplastic with high a reinforcement content, water stability, and toughness is reported. Lignin-containing cellulose nanofibers (LCNF) were prepared by pretreating eucalyptus wood powder with a deep eutectic solvent and high-pressure homogenization. Then, the pre-synthesized ε-caprolactone oligomers were in-situ polymerized in LCNF. The interaction of LCNF with ε-caprolactone-oligomers in the LCNF-crosslinked polycaprolactone (LCNF-PCL) bioplastic resulted in excellent mechanical properties (tensile strength: 76.59 MPa; toughness: 9.82 MJ m^-3). The LCNF-PCL bioplastic also demonstrated excellent water stability (wet tensile strength: 34.21 MPa; water absorption: <5 %), thermal stability, and UV protection. This approach may provide a potential method for utilizing lignocellulosic resources to develop environmentally friendly bioplastics with good toughness and water stability.