Toxic Gas-Free Synthesis of Extremely Negative Triboelectric Sulfur Copolymer Blends Via Phase Separation of Fluorine-Rich Polymers

Recently, we reported surface fluorination of sulfur-based polymers to introduce a new class of extremely negative triboelectric material. However, the direct surface fluorination requires the use of toxic fluorine gas. In this study, we report the toxic gas-free synthesis of extremely negative triboelectric sulfur-rich polymers via the phase separation of a fluorine-rich polymer, poly(2,3,4,5,6-pentafluorostyrene) (PPFS), from sulfur copolymers. PPFS was physically mixed in situ during the inverse vulcanization of elemental sulfur, a by-product of petroleum refining to prepare the polymer blends. Hot pressing of the blends into films induced the phase separation of the hydrophobic PPFS; subsequently, PPFS migrates to the hydrophobic air interface to minimize the interfacial energy. A triboelectric nanogenerator (TENG) based on the phase separated blend films presented long-term stable voltage and current outputs that are 8-fold and 9-fold higher, respectively, than those of a TENG based on polytetrafluoroethylene (PTFE), a well-known extremely negative triboelectric polymer. We also demonstrate the ability of a TENG based on an 81.1 cm2-sized blend film to power 400 series-connected blue LEDs of 3.3 V; a triboelectric open-circuit voltage output of 1362.4 V is obtained under a minimal force of 30 N. The demonstrated phase-separation strategy for fluorine-rich polymers will thus provide insights for achieving low-cost, environment-friendly, and high-performance triboelectric energy harvesting.