Optoelectrical, morphological and mechanical features of nitrophenyl supported poly(1,3,4-oxadiazole)s and their nanocomposites with TiO2

Abstract

Two nitro phenyl supported poly(1,3,4-oxadiazole)s viz.; poly(pyridine(2-nitrophenyl)-1,3,4-oxadiazole) [PPNO] and poly(2-(o-nitrophenyl)-5-phenyl-1,3,4-oxadiazole) [PNPPO] were initially synthesized by a dehydrocyclization reaction, and then reinforced with TiO₂ nanoparticles. They were characterized in terms of optoelectrical, morphological and mechanical properties in order to examine their suitability to function as active or electron transport layers in polymer light emitting diodes (PLEDs). The nanocomposites have been found to possess charge transfer characteristics from the macromolecular systems (PPNO or PNPPO) to TiO₂ particles, upon photo-excitation. Cyclic voltammetric examinations indicated a reduction in band gap for PPNO and PNPPO in the presence of TiO₂ nanoparticles. The nonlinear optical responses and optical limiting behavior of PPNO, PNPPO and their nanocomposites were also evaluated by the Z-scan technique, using nanosecond Nd:YAG, 532 nm laser radiations. In view of user-friendly device fabrication, flexible films of PPNO and PNPPO were fabricated by blending the composites with 2 wt% of poly(methylmethacrylate). Along with good mechanical properties, PPNO and PNPPO showed high fluorescent quantum yield, presenting them as promising candidates for PLED fabrication. Interestingly, the current–voltage (I–V) characteristics propose their additional application as semiconducting packaging materials for optoelectronic devices.