Thermally-stimulated depolarization current studies in chemically doped poly(2,6-dimethyl-1,4-phenylene oxide)

Abstract

The electret properties of solution-grown poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) films doped with 7,7,8,8-tetracyanoquinodimethane, tetracyanoethylene, 2,4,7-trinitro-9-fluorenone and I 2 have been studied by measuring thermally-stimulated depolarization currents (TSDC) as a function of dopant concentration varying from 0.25 to 1.00 wt% for identical conditions of polarizing field, temperature and time. The depolarization behaviour of poled doped PPO film exhibits a dopant-concentration dependent single relaxation around 438 K maximum in the TSDC spectra. This is attributed to formation of charge-transfer complexes with the PPO chain by interstitially placed dopants. The existence of such a complex is confirmed by ultraviolet-visible and infrared absorption spectral measurements. The dopant-concentration dependent increase in the magnitude of the TSDC peak is attributed to the enhanced aligned dipole density.