Synthesis and optoelectric properties of polymers containing phenylenevinylene units

Abstract

Poly(2-(2′(-ethylhexylthio)-5-methoxy-1,4-phenylenevinylene) (PMEHTPV) was synthesized in thin films via water-soluble precursor polymer and characterized with thermogravimetric analysis (TGA), FT-IR, and elemental analysis, etc. The PMEHTPV film could be stretched up to 10 times and showed conductivity of 0.13 $Scm^{-1}$ when doped with $FeCl_3$. The 2-ethylhexylthio group resulted in blue-shifted absorption and emission compared to those of poly (2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The relative quantum efficiency of the device made by PMEHTPV was 20 times higher than that of MEH-PPV. A novel poly(1,4-phenylenevinylene) (PPV) derivative containing nonlinear optical (NLO) moiety was synthesized via the methoxy-precursor pathway to give a highly rigid structure which still maintained good processability. Poly(2-butoxy-5-(2-{ethyl-[4-(4-nitrophenyldiazenyl)-phenyl]-amino} -ethoxy)-1,4-phenylene vinylene) (PBDR1PV), containing a Disperse Red 1 (DR1)-type chromophore, was characterized by conventional spectroscopic methods (UV-visible, FT-IR, NMR) and by thermal analyses. The synthetic approach has been applied for the preparation of high optical quality films for nonlinear optical applications. PBDR1PV films showed a high resonant $d_{33}$ value of 50pm/V when measured using second harmonic generation (SHG) method. The nonlinearity of PBDR1PV was very stable at 90℃ for a month without detectable loss. In addition to the second-order NLO properties, the PBDR1PV film showed third-order NLO properties simultaneously and the measured $χ^{(3)}$ value was found to be $2.5×10^{-12}$ esu. Three polyimides containing nonlinear optical (NLO) chromophore were prepared through a new synthetic pathway. Coupling of dihydroxy and diimide compounds yields the polyimide. Due to the mild condition of polymerization, chemically labile hemicyanine dye could be incorporated in the polyimide backbone successfully. The molecular weights of obtained polyimi...