Preparation of conducting polymer composites by solid state polymerization of 2,5-dibromo-3,4-ethylenedioxythiophene

Abstract

Conducting polymer composites containing poly(3,4-ethylenedioxythiophene) (PEDOT) was prepared by solid state polymerization (SSP) of 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) in the presence of either polystyrene (PS) or polybutadiene (PB) matrix. The percentage yield of up to 85% of the PEDOT could be obtained. The presence of PEDOT in the polymer composite was verified by FT-IR spectroscopy, UV-VIS spectroscopy, TGA, and XRD. As measured by four-point probe conductometer, the conductivity of the PEDOT/PS composite film can reach as high as 58 S/cm. The optimal condition to obtain the highest conductivity of the PEDOT/PS composite was to use 3:1 DBEDOT:PS weight ratio, 0.225 g/mL of DBEDOT and conducting the SSP at 50℃ for 7 h. The PEDOT/PB composite films possess significantly lower conductivities than the PEDOT/PS composite film. It is believed that the low Tg of PB allows the DBEDOT as well as PEDOT to move during SSP and resulting in the PEDOT with less ordered conformation and lower conductivity. The conductivity of the PEDOT composite films was found to decrease upon storage due to the loss of Br₂. The conductivity can be completely recovered after re-doping with I₂ in the case of PEDOT/PS composite films but cannot be recovered in the case of PEDOT/PB composite films.