New poly(p-phenylenevinylene) derivatives containing isosorbide unit in the side-chain

New conjugated PPV derivatives containing the chiral isosorbide group (P1-3) have been synthesized via the Gilch reaction. The polymers are optically active, soluble in common organic solvents and show good film-forming abilities. High number-average molecular weights were determined by size exclusion chromatography (SEC) (16•103–21•103 g•mol–1). The molecular structures of the polymers were confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. Thermogravimetric analysis of the polymers showed good thermal stability up to 320°C. The optical properties of these π-conjugated materials were investigated by UV-vis absorption and photoluminescence (PL) spectroscopies. The polymers show a yellow fluorescence in dilute solution, and an orange emission is observed in thin films. The introduction of the polar isosorbide groups improved the PL intensity, and quantum yields between 50 and 73% were obtained. The HOMO-LUMO energy levels were estimated by cyclic voltammetry, and the electrochemical gaps were 1.81, 1.83 and 2.48 eV for P1, P2 and P3, respectively. Single-layer diode devices were fabricated and show relatively low turn-on voltages between 3.1 and 3.4 V