Humidity sensitive poly(2,5-dimethoxyaniline)/WO3 composites

Humidity sensitive poly(2,5-dimethoxyaniline)/WO3 (PDMA/WO3) composites with different weight percents of WO3 have been prepared by a simple mechanical mixing method. These composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Humidity sensing characteristics, including the resistance versus relative humidity (RH), humidity hysteresis, response time, repeatability and long-term stability of these composites have been investigated. The PDMA/WO3 composites show better sensing properties than pure PDMA, such as higher sensitivity, quicker response and small hysteresis. The resistance of the composite with 30 wt% of WO3 changes linearly over the humidity range (23–84% RH). Furthermore, it exhibits a maximum percentage response factor (∼651 at 87% RH), quick response (humidification, 27 s and desiccation, 136 s), narrow hysteresis (∼5%) and an excellent repeatability of the response.