Humidity Sensor Using Chemically Synthesized Poly(1,5-diaminonaphthalene) Doped with Carbon

The chemically synthesized poly(1,5‐diaminonaphthalene) (DAN) doped with carbon was applied to a humidity sensor. The polymer was characterized using Fourier tranform infrared, ultraviolet‐visible spectrometry, and cyclic voltammetry. The composite polymer film was prepared by mixing the poly(1,5‐DAN) powder with acetylene carbon black in various ratios and 6.0 wt % polyvinylidene fluoride in N ‐methylpyrrolidone. The composite polymer sensor was examined and applied to the amperometric and the resistance‐type humidity sensor employing chronoamperometry and impedance spectrometry. The relative humidity was controlled using the standard saturated salt solutions at 20 ± 0.1°C. Under optimized experimental conditions, the calibration plot for the 15:1 composition sensor showed a straight line over the entire measured range of percent relative humidity (RH) without hysteresis. The overall sensitivity was calculated as S =[R(93% RH) − R(12% RH)]/R(93% RH). The current drift was less than ±1% for the lower humidity.