Tetraphenylthiophene–thiazole-based π-conjugated polyazomethines: synthesis, characterization and gas sensing application

Abstract

2,5-Bis(4-(2-aminothiazole) phenyl)-3 and 4-diphenyltetraphenyl thiophene (TPTPThDA) are fine processed in three steps. A series of polyazomethines containing thiophene–thiazole unit have been incorporated by the polycondensation of a new diamine, i.e. TPTPThDA, with proportionate of aromatic dialdehydes. The impact of insertion of thiazole entity in the polyazomethine matrix with the azo linkages having dialdehydes [isophthalaldehyde (1,3 IPA) and terephthalaldehyde (1,4 TPA)], on conductivity and gas sensing properties, has been studied. In all polyazomethines synthesized (PAM-01 to PAM-05), the preeminent in terms of conductivity and gas sensing properties has been established to be the PAM-03 containing polyazomethine matrix composition of 1,3 IPA and 1,4 TPA with thiophene–thiazole unit. After the infusion with the dialdehyde comonomers, an inflation of the molecular weight and the polyazomethines films were highly selective towards H2S gas at 35 °C with great sensitivity and acceptable selectivity. Along this, all polyazomethines have Tg in the range of 257–260 °C and T10% value of all thermally stable polyazomethines in air and nitrogen was in between of 458–545 °C and 527–601 °C, respectively. The polymer backbone contains rigid framework expect PAM-05, and due to this, they show less solubility in organic solvents. XRD study confirms that all the polyazomethines are amorphous in nature having broad peak in the range of 20°. The UV at 342 nm shows that there is a formation of imine (–C=N–) linkages in the polymer matrix which is helpful for the conduction of electron throughout. The band gap energy of PAM-3 is found as 3.63 eV.