Chitin–polyaniline blend as humidity sensor

A new processable and humidity sensitive chitin–polyaniline blend has been developed. Polyaniline is blended with chitin by solution blending method. The free standing films of blends are stable under ambient condition. The characterization of the blends is done by UV–vis absorption spectrum, FTIR, conductivity studies, thermogravimetric analysis and SEM. Conductivity of the self-doped blends increases from less than ≈10−7 S/cm to 2.15 × 10−5 S/cm, depending on the percentage of polyaniline in the blend. When these blends are doped with HCl conductivity rises to ≈9.68 × 10−2 S/cm. Spectroscopic analysis shows interaction between chitin and polyaniline and the electronic states are similar to those of the emeraldine and protonically doped forms of polyaniline. These blend films are used for the construction of resistive based humidity sensor. A linear response of resistance with humidity is observed. It shows a small hysteresis and its response is stable even after 75 cycles of humidity exposure. Effect of electron beam irradiation on the humidity response has also been studied. Sensitivity is improved upon irradiation and doping. Further effect of thickness and electrode separation on humidity response is also studied. Response time for the humidity sensor is less than 30 s. The constructed humidity sensor shows good results in the 10–100% humidity and in the temperature range of 20–60 °C.