Synthesis, optical properties, and characterization of new soluble conjugated poly(p-phenylenevinylene) derivatives constituted of alternating pyrazole and 1,3,4-oxadiazole moieties

Two new soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main core were successfully synthesized by 1,3-dipolar addition, dehydration, and Heck coupling reaction. The new conjugated polymers are soluble in common organic solvents afforded by the fully conjugated backbone with soluble dedecyloxy side groups. The polymers showed relatively high glass-transition temperatures (∼150°C) and good satisfactory thermal stability. Solutions of the polymers emitted bluish-green light with photoluminescence (PL) emission maxima around 530-540 nm. The PL spectrum for polymers of thin films, with a maximum at 570 nm, shows a red-shift (∼35 nm) with respect to the solution spectrum. Cyclic voltammetry displayed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n-type electroluminescent materials. The electron affinity of new polymers was estimated as 2.76-2.81 eV. The weight-average molecular weights (M_w) of the new soluble polymers were in the range 3400 - 3500.