Synthesis, Characterization, and Electrical and Thermal Stability of Semiconducting π-Conjugated Polyazomethines Containing a Tetraphenylthiophene-Oxazole Unit

Abstract

A series of polyazomethines (PAM-01, PAM-02, PAM-03) containing various amounts of tetraphenylthiophene-oxazole (TPTP-o) moieties were produced by the polycondensation of a diamine precursor (TPTP-o) with equimolar proportions of two aromatic dialdehydes [isophthalaldehyde (1,3 IPA) and terephthalaldehyde (1,4 TPA)]. The TPTP-o precursor was successfully synthesized in three steps. The synthesized TPTP-o and the polymers (PAM-01, PAM-02, PAM-03) were characterized by ultraviolet–visible (UV–Vis) spectroscopy, FT-IR spectroscopy, x-ray diffraction (XRD), 1H-NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The effects of the TPTP-o units in the PAM on the insertion with azo linkages were studied with respect to conductivity and thermal stability. The room-temperature DC electrical conductivity of the PAM films was found to range from 9.59 × 10−7 S/cm to 9.73 × 10−7 S/cm. UV absorption at 342 nm confirmed the formation of azo (–C=N–) linkages in the polymer, which is helpful for electron conductivity throughout the polymer network. All three PAMs had a glass transition temperature (Tg) between 260°C and 267°C, and T10% thermal degradation values of thermally stable polyazomethines were in the range of 517–530°C. All three PAMs showed moderate solubility in organic solvents and inherent viscosity of between 0.31 dL/g and 0.35 dL/g. The XRD study indicated that all three PAMs were amorphous in nature, with a broad peak in the vicinity of 20°.