Solid state electrical conductivity and thermal degradation studies on some phenothiazine derivatives

Electrical conductivity and thermal degradation studies of promethazine hydrochloride (PH); 2-chlorophenothiazine (CP); diethazine hydrochloride (DH) and trifluoperazine dihydrochloride (TFP) are reported. The activation energies are evaluated based on their electrical conductivity study conducted over the temperature range 30-150 °C. These energies for PH, CP, DH and TFP are found to be 0.86, 1.02, 0.68 and 1.08 eV, respectively. The materials are analyzed for the kinetic parameters like the activation energies for decomposition and the Arrhenious pre-exponential factors in their pyrolysis region using Broido's, Coats-Redfern and Horowitz-Metzger methods. Using these factors and the standard equations thermodynamic parameters such as enthalpy, entropy and free energies are calculated. Thermogravimetric study on these phenothiazine derivatives in air indicated that their stabilities are in the order CP>TFP>PH >DH.