Synthesis and characterization of poly(o-toluidine)/kaolinite conductive composites for humidity and temperature sensing

Abstract

Conductive poly(o-toluidine)/kaolinite composite was synthesized via chemical polymerization of o-toluidine in the availability of kaolinite using ammonium persulfate as oxidizing agent. To investigate the use of the prepared conductive composite as humidity and temperature sensor, the effect of polymerization conditions such as HCl, o-toluidine and oxidant concentrations on the amount of conductive POT contained in the composite and the conductivity values of composites were investigated. It was found that the composites with the highest poly(o-toluidine) content (29.4%) and conductivity (8.3x10(-4) Scm(-1)) were obtained by 0.2 M ammonium persulfate, 0.4 M o-toluidine and 1 M hydrochloric acid for 2 hours of continuous polymerization at 20 degrees C. The resistivity values of pure poly(o-toluidine) and poly (o-toluidine)/kaolinite composite were monitored during heatingcooling cycles in the range of 0-100 degrees C. Changes in resistivity for pure poly(o-toluidine) and poly(o-toluidine)/kaolinite composite with humidity 30-90% were examined and humidity sensor behavior was determined. Characterization of the prepared composite was performed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy techniques (SEM).