Physical properties of solution cast poly(styrene–butadiene–styrene)/heteroaromatic poly(azo-thiourea) blends

The heteroaromatic azo-polymer poly(azo-thiourea) has been prepared using 4-(4-aminobenzyl)benzenamine and diazonium salt solution of 2,6-diaminopyridine. The polymer was processable using polar organic solvents and had high molar mass of 62 × 10³ gmol⁻¹. Various concentrations of azo-filler were blended in solution phase using tetrahydrofuran or dimethylformamide with poly(styrene–butadiene–styrene). Morphology, thermal, and mechanical properties of styrene–butadiene–styrene/poly(azo-thiourea)blends have been studied using field-emission scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and tensile tests. Field-emission scanning electron microscopy micrographs of styrene–butadiene–styrene/poly(azo-thiourea) blends revealed fine granular filler dispersion in the matrix and development of conducting pathways. Accordingly, filler content from 10 to 60 wt% increased the conductivity from 0.99 × 10⁻¹ to 1.61 S cm⁻¹. A relationship between poly(azo-thiourea) loading and thermal stability of the materials was evident. Temperature for 10 wt% thermogravimetric weight loss increased from 467℃ to 483℃, while glass transition was enhanced from 151℃ to 155℃. Thermal and conductivity properties showed better results relative to pristine elastomer but less significant than the conducting filler used. Tensile properties were also dependent on the solvent used. In the dimethylformamide cast system, elongation at break was 345–387% versus the tetrahydrofuran system at 33–38%. The dimethylformamide cast blends tensile modulus was 599–769 MPa versus 876–1032 MPa for the tetrahydrofuran system. Thermal and conductivity behaviors were the same for both hybrid systems. Stress-induced birefringence in these blends has also been studied to find out the suitability of materials for waveguide applications.