High performance heteroaromatic poly(azo-ester)s and their miscible blends: Thermomechanical and conductivity profile

An interesting type of thermally stable and processable poly(azo-ester)s (PAEs) have been synthesized through the polycondensation of a novel diol—(E)-1-(5-(3-hydroxypyridylazo)thiocarbamoyl-aminonaphthyl)-3-(3-hydroxypyridylazo)thiourea, and various diacid chlorides. The dihydroxy compound containing azo group (−N=N−) was prepared via multi-step procedure in which the coupling of bisthiourea compound with diazonium chloride (in alkali) yielded the desired monomer. The polymeric materials were characterized in terms of FTIR, 1H NMR, solubility, solution viscosity, molecular weight, electrical conductivity, glass transition and thermal degradation temperatures. PAEs possessed high inherent viscosity 1.19–1.23 dL/g and molar mass (8.3–8.5) × 104. The polymers were thermally stable in the range 531–541°C (10% gravimetric loss T10) having Tg′ = 258–266°C. PAEs were, thus, melt blended with polyaniline resulting in high performance materials that potentially combined the fine thermal properties and processability of poly(azo-ester)s with electrical characteristics of polyaniline. The miscible blends exhibited good heat stability (T10 = 525–527°C, Tg = 246–252°C) and mechanical strength (61.81–63.19 MPa) compared with several polyaniline-based blends. FESEM showed nano-level homogeneity of the microstructure liable for better electrical conductivity (3.2–4.2 S/cm).