Physical properties of poly[(thiophene-2,5-diyl)-co-para-chloro benzylidene] doped with cobalt sulphate: synthesis and characterization

Conjugated poly[(thiophene-2,5-diyl)-co-para-chloro benzylidene] has been synthesized by a simple condensation method. Condensation of thiophene with para chloro benzaldehyde catalyzed by POCl₃ in 1,4 dioxane neutral solvent and reaction was carried out at low temperature (87 °C) for 30 h. After completion of the reaction, 5–10 ml ammonia to remove the catalyst and 100 ml methanol was added to obtain the product. Doping effect on the polymer was also analyzed using different characterization techniques such as: UV–Vis, FTIR, ¹HNMR, ¹³CNMR, XRD, FE-SEM, EDX, BET, DSC. The result reveals that the yield of doped poly[(thiophene-2,5-diyl)-co-p-chloro benzylidene] is relatively good using POCl₃ as a dehydrating agent using single-step polymerization. Structural analysis confirmed the formation of polycrystalline phase. The surface morphology of undoped complex showed the nanoporous structure, consisting of nano sheets which were interconnected with each other. XRD pattern confirms that the synthesized material is in nano crystalline form. Doping with cobalt sulphate resulted in porous structure with increase in surface area value from 2400 to 3300 cm²/g. DSC analysis reveals that the samples are thermally stable up to 300 °C. From optical absorption, the band gap is calculated and observed to be around 2.68 and 2.87 eV and conductivity values of 1.99 × 10⁻⁷ and 9.63 × 10⁻⁸ S/cm using two-probe method for undoped and doped samples and hence it can be used in many applications as a good semi-conducting material.