In this work, the polymeric ionic liquid (PIL)/ polybenzimidazole (PBI) composites (PIL/PBIs) based humidity sensors were prepared. The humidity sensing properties of the sensors were controlled by the ratio of PIL and PBI in the sensing films, and the optimized sensor performs a high response of 988.1 in the low humidity range (2%−35% RH). The introduction of PBI into sensing film can guarantee the stability of the humidity sensors. The as-prepared sensor can be utilized to detect the moisture in lubricating oil.
In recent years, poly(ionic liquid)s (PILs) have attracted much attention for the application in humidity sensors. However, the ionic conductivity of PILs is inhibited in the low humidity range. In this work, discontinuous conductive template was prepared using a hydrophobic conductive polymer PEDOT:F, and PILs was prepared in situ on the conductive template (PFCT&PILs) to obtain a low humidity sensor. The prepared PFCT&PILs sensor has much lower impedance value, higher response and smaller detection limit than the pure PILs sensor. The PFCT&PILs sensor shows a high response of 208, with a small hysteresis of 0.5 % RH and has small impedance value in 5 %–35 % RH. The humidity sensitive principle of PFCT&PILs sensor has been discussed.