Electrically Conductive Graphene-Based Biodegradable Polymer Composite Films with High Thermal Stability and Flexibility

Cellulose nanofibril (CNF) and graphene (GR) powder were added into polylactic acid (PLA)/ polypyrrole (PPy) composite films via a low-cost, eco-friendly, low-temperature, and in-situ polymerization synthesis, which obtain novel flexible and conductive polylacticacid-cellulose nanofibril-graphene/polypyrrole (PLA-CNF-GR/PPy) composite films. The CNF was embedded in the PLA matrix to enhance the mechanical properties. Remarkably, when a few GR (1%) powder was added, the tensile strength of composite films increased by 5.6%, respectively, compared with pure PLA-CNF, and increased by 17.6% compared with the PLA. The GR and CNF had a positive influence on mechanical properties of composite films. In addition, the PLA-CNF-GR/PPy composite films exhibited many unique properties when GR powder was introduced, including high thermal stability, and especially electrical conductivity. The electrical conductivity of the PLA-CNF-GR/PPy composite films increased from 0.12 to 1.06 S/cm as the content of GR powder increased from 0 to 10%. The PLA-CNF-GR-10/PPy also demonstrated excellent flexible stability, only 7.5% deviation after over 100 bending cycles. Furthermore, we designed and found that the exploration of a flexible solid-state supercapacitor assembled with PLA-CNF-GR-10/PPy composite electrodes had a capacitance of 30 F/g at a current density of 0.5 A/g. Although it was not quite as prominent as the capacitance, it provided an innovative means for preparing the conductive composite films. Based on these advantages the PLA-CNFGR/PPy could be considered as sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of biodegradable materials.