Conductivity, optical absorption, photoluminescence, and X-band optically detected magnetic resonance of novel poly(2,5-dibutoxyparaphenyleneacetylene) (PDBOPA)

Abstract The optical properties of novel PDBOPA (average molecular weight ≈ 48 000) are described and discussed. Exposure to I 2 vapor at ≈80 °C increases the conductivity to ≈5 × 10 −3 S/cm, but the I 2 rapidly evolves from the film at room temperature. The absorption onsets at 2.53 eV and peaks at 2.81 eV. The 2.71 eV-excited photoluminescence (PL) peaks at ≈2.0 eV in films and solutions. In all cases, it is very intense and largely structureless. This contrasts with the clear vibronic structure of the PL of poly(3-alkylthiophene) (P3AT) and poly(2,5-dialkoxy para phenylenevinylene) (PDOPV) films and blends. As in P3AT and PDOPV, three PL-enhancing optically detected magnetic resonance (ODMR) features are observed: (i) a strong narrow (≈15 G wide) resonance at g = 2.0025, attributed to intrachain polaron recombination; (ii) a ≈1.0 kG wide triplet powder pattern around g ∼ 2, and (iii) the Δm s = 2 transitions of these excitons at g≊4.07 . The results are discussed in relation to conformational defects resulting from the near cylindrical symmetry of the backbone acetylene units.