Effects of a tert ‐butylphenylene substituent on the structure and optical, fluorescent and thermal properties of the poly( p ‐phenylenevinylene) derivatives

Two soluble fluorescent polymers, poly(2‐decyloxy‐5‐(4′‐ tert ‐butylphenyl)‐1,4‐phenylenevinylene) (DtBP‐PPV) and poly(2‐decyloxy‐1,4‐phenylenevinylene) (DO‐PPV), were prepared by a method similar to the Gilch procedure. The DtBP‐PPV and DO‐PPV have a same chemical structure except for the conjugated tert ‐bytulphenyl substituents in the former. The polymers are characterized by using 1 H NMR, FTIR, UV–vis, photoluminescence (PL), and electroluminescence (EL) spectroscopies and thermogravimetric analysis (TGA). The 1 H NMR spectra show no tolane‐bis‐benzyl (TBB) structure defects in DtBP‐PPV but some in DO‐PPV. Both UV–vis absorption and PL emission peaks of the DtBP‐PPV exhibit a red‐shift phenomenon as compared with those of the DO‐PPV. Moreover, with the DtBP‐PPV and DO‐PPV acting as light‐emitting polymers separately, EL devices were fabricated with a sequential lamination of ITO/PEDOT/DtBP‐PPV (or DO‐PPV)/Ca/Ag. The DtBP‐PPV‐based device shows a lower turn‐on voltage, a longer EL emission wavelength, and a higher brightness than the DO‐PPV‐based device. The maximum brightness of DtBP‐PPV‐based device is 57 cd/m 2 at an applied voltage of 12 V. POLYM. ENG. SCI., 47:1380–1387, 2007. © 2007 Society of Plastics Engineers