Proposing poly(3-hexylthiophene) as a naked-eye discharge indicator for high voltage applications†

Polymeric insulating structures in power equipment inevitably deteriorate under long-term operation, initiating unobservable partial discharge, which develops into breakdown and insulation failure, resulting in large-area power shutdown, causing huge economic losses. Currently, the detection of early discharge relies on optical fiber sensing, ultrasound, etc., which requires additional electrical signal access or complex equipment. Herein, poly(3-hexylthiophene) (P3HT) is functionalized as a flexible naked-eye discharge indicator through color changes by discharge triggered oxidation. The high voltage discharge generates active oxygen radicals, which oxidize H_α on the P3HT side-chain and C_α on the thiophene ring, leading to breakage of the side-chain and backbone, as well as thiophene ring opening, resulting in crystallinity changes from highly regular edge-on to amorphous configuration, giving rise to an observable color change. The vertical dielectric performances of P3HT and typical non-conjugated polymer composite films are highly sustained, which is further potentially applied in the quantitative evaluation of fault discharge in a power cable branch box under operation. Based on the huge amount of power equipment worldwide, this approach may not only broaden the application of P3HT in the power industry, but could also boost the demand for such conjugated polymers from organic electronics towards massively applied commodity chemicals.