Alkoxy-substituted poly(p-phenylene1,3,4-oxadiazole)s: synthesis, chemical characterisation and electro-optical properties

The synthesis of a series of conjugated aromatic polyoxadiazoles (PODn) characterised by having moderate chain flexibility and highly flexible lateral substituents is reported. The majority of these polymers are soluble in a mixture of chloroform and trifluoroacetic acid, and have inherent viscosities up to 0.9 dL/g. The glass transition temperature, Tg, lies in the range 165-230 °C and depend on the side chain length. The PODn show a good thermal stability in nitrogen up to 270 °C. Wide angle X-ray diffractograms reveal a “comb-like” organisation of the polymeric chains. Homogeneous thin films of such a material were prepared by the spin-coating technique. Films spun on silica fused were characterised by spectroscopic analysis in the whole UV-VIS-NIR range showing a high transmission in the NIR region which is the typical telecommunication band (1300-1500 nm). Furthermore, the refractive index and the film thickness have been measured using the coupled modes technique in a planar guiding structure having POD as the core. It has then been prepared a device consisting of the said polymer sandwiched between two electrodes on top of a glass substrate. The electron conductivity of the polymer has been found to be higher than that of terephthalic poly(1,3,4-oxadiazole).