Evolution with time of properties of the polytetrabromo-p phenylenediselenide doped with an halogen (Cl or I).

Summary form only given. PBrPdSe has been doped by chlorine or iodine. The samples have been studied by X ray photoelectron spectroscopy (XPS), electron spin resonance (E.S.R.) and with a scanning electron microscope equiped with an electronic microprobe. Conductivity measurements have also been performed on pressed pellet samples, at room temperature. In the case of chlorine doped polymer, it is shown by XPS study that chlorine decomposes progressively the polymer. This result is corrobored by ESR study. The conductivity of the I/sub 2/ doped PBrPdSe exhibits an increase by about three orders of magnitude. The doping concentration decreases with time from 30 at % to 5 at % but the ESR signal stays the same. The high value of g anisotropy and the XPS peak of Se show that the positive charge is localized on the Se atoms. The binding energy of the iodine anion corresponds to I/sup - //sub 5/ species after doping and to I/sup -/sub 3/ thirteen months later. All these results can be explained by the reaction I/sup -//sub 5/ /spl rarr/I/sub 2/ + I/sup -//sub 3/. The I/sub 2/ removing explains the decrease of the iodine concentration and the I/sup -//sub 3/ formation explains the 3 stability of the ESR signal. The microphotograph show that the surface of the fibrils of iodine doped powder become rough with time this may be explained by I/sub 2/ removing and surface modification. These modifications can explain the decrease with time of the conductivity.