Synthesis and electrical properties of poly (2-methoxy-1, 4-phenylene vinylene) and PPV copoymers

Abstract

Asymmetrically substituted poly (2-methoxy-1,4-phenylene vinylene) and PPV copolymers were synthesized via water-soluble precursor route. Sythesized polymers were characterized by NMR, thermogravimetry (TGA, DSC), IR and UVVIS spectrophotometry. The actual compositions of the copolymers were determined by elemental analysis. And their electrical conductivities were measured by four-probe method at room temperature after $I_2$ or $FeCl_3$ doping. The more portion of PPV polymers contained, the higher conductivity they appeared. The conductivity of $I_2$ doped PMPV (undrawn) was 1.3 S/cm. The maximum conductivity of $FeCl_3$ doped PMPV was 4.0 S/cm and copolymers ranged from $10^{-1}-10^2$S/cm. For all the samples, conductivity increased with temperature, which is usually observed for semiconductors. Activation energy for conduction was estimated from the Arrehenius plot of log(R) versus $T^{-1}$. Activation energy of $FeCl_3$ doped PMPV (stretched) was 96 meV. The conductivity data were plotted against $T^{-1/4}$ and each curves showed a straight line relation. Such behavior is expected for the systems where variable range hopping mechanism applies. $x^{(3)}$ value of PMPV was measured by degenerate four-wave mixing (DFWM) technique and calculated value was $6.9\times10^{-10}$ esu at 602 nm.