Synthesis and investigation of the structure, thermal, optical, and electrical properties of poly (indol-thiazolo-thiadiazole) derivatives at room temperature

Abstract

This research work is intended for the novel synthesis and study of structural, thermal, optical, electrical, and dielectric properties of semiconductor poly (2-amino-5-(1H-indolyl)-5H-thiazolo[4,3-b]-1,3,4-thiadiazole) (PAITTD) and its N-substituted indole derivatives with a side chain containing chlorobenzoyl (PACBITTD) and bromobenzene sulphonyl (PABBSITTD). The characterization techniques such as H1NMR, FTIR, SEM, and TGA/DSC ensured the structural and thermal properties of the as-synthesized polymers. In addition, the molecular weight of the PAITTD, PACBITTID, and PABBSITTD was calculated via H1NMR technique. The optical band gap as obtained from the absorbance study was found to be in the range of 1.5 eV to 2.58 Ev. Moreover, the ground-state geometries and the absorption wavelengths for the studied compounds were investigated by DFT and TD-DFT, where the theoretical results show coincidence with these of the experimental where the calculated (λmax) values are approximately near to the experimental (λmax) values for the PAITTD, PACBITTID, and PABBSITTD. The impedance ac conductivity and dielectric properties of the PAITTD, PACBITTID, and PABBSITTD were performed in the frequency ranges from 20 Hz to 10 MHz at room temperature, where their values were 3.0 × 10−7, 8.7 × 10−7, and 2.6 × 10−6, respectively. The Nyquist plot confirmed the presence of both grain and grain boundary effects for conducting PAITTD, PACBITTID, and PABBSITTD, and Double relaxation behavior was also observed. The variation of ac conductivity with frequency obeys the modification of Jonscher’s universal power law (JUPL). Based on the optical and electrical properties, synthetic PAITTD, PACBITTID, and PABBSITTD are promising materials in the design of optoelectronic semiconductor devices.