Eco-friendly and recyclable thermosetting polyurethane composites for human motion monitoring

Designing and developing friction layer materials that are environmentally friendly and recyclable is key to preparing triboelectric nanogenerators (TENG). Herein, a recyclable friction layer material, CFPU-X, has been introduced. This material is dynamically crosslinked through a Diels-Alder reaction between a polyurethane (MPU) containing maleimide groups and carboxylated cellulose nanocrystals with furan groups. The reaction enhanced the cross-linking degree of polyurethane, resulting in a significant increase in tensile strength, with CFPU-15 exhibiting a maximum value of 18.18 MPa, a 761.61% improvement over MPU. Notably, CFPU-9 demonstrated self-toughening properties, possibly attributed to the growth of molecular chains in the same space after heating and redissolution. This resulted in an increase in hydrogen bonding content and a more compact reconfigured crosslinked network, leading to a 145.83% increase in elongation at break. The CFPU-12 TENG is expected to be utilized in medical diagnostics, motion analysis, and health monitoring. This study offers worthy ideas for the development of recyclable materials for high-performance, flexible energy harvesters.