Synthesis, and electrical, nonlinear optical and luminescent properties of novel poly (1,4-phenylenevinylene) derivatives

Abstract

A new class of poly(1,4-phenylenevinylene) derivatives were synthesized through processible precursor polymers. The electrical conductivities of synthesized polymers were measured by four-probe method at room temperature after doping with $I_2$ or $FeCl_3$. The synthesized polymers showed their electrical conductivities between $10^{-4}$-$10^2$ S/cm depending on nature of substituent, copolymer composition and draw ratio, etc. The third-order nonlinear optical susceptibilities of the polymer films were determined by degenerate four-wave mixing (DFWM) measurement technique at 602 nm, and also third-harmonic generation (THG) method at 1907 nm. The calculated $\chi^{(3)}$ ($-\omega$;$\omega$,$\omega$,$-\omega$) values of the polymers by DFWM method were ranged from $10^{-11}$ to $10^{-10}$ esu, and $\chi^{(3)}$ (-3$\omega$;$\omega$,$\omega$,$\omega$) values by THG method were ranged from $10^{-13}$ to $10^{-12}$ esu. The electro-optic properties of polymer films containing electron-donating methoxy and electron-withdrawing nitrile group substituted stilbene moiety were investigated using reflection measurement technique, after corona discharge poling under high electric field. They showed electrooptic coefficients of $1.2\,\pm\,0.3$ pm/V. No significant decay of the electrooptic responses was observed for over 2600 h at room temperature. Most significant is the fact that these polymers showed no detectable decay and no tendency of relaxation for 150 h even at $100^\circ C$. Blue light-emitting polymers with well-defined conjugation length were also synthesized through Wittig polycondensation reaction. The simple light-emitting devices (LED) of these polymers were made with ITO and aluminum as positive and negative electrode. The electro-luminescent (EL) properties of these polymers were studied by current-voltage characteristics, EL spectra and light intensity-current characteristics.