Alcoxy-substituted poly (p-phenylene 1, 3, 4-oxadiazole)s: synthesis, chemical characterisation and electro-optical properties

The synthesis of a series of coniugated 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 depends on the side-chain length. The PODn show a good thermal stability in hydrogen up to 270°C. Wide angle X-ray diffractograms reveal a "comblike" organisation of the polymeric chains. Homogeneous thin films of such a material were prepared by the spincoating technique. Films spun on fused silica were characterised by spectroscopic analysis in the whole UV-Visible 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).