A comparison of experimental and theoretical studies of benzoquinone modified poly(thiophene): effect of polymerization techniques on the structure and properties

The present manuscript reports the synthesis of benzoquinone (BQ) modified polythiophene (PTh) by chemical and microwave-assisted polymerization techniques. The synthesized oligomers were investigated for their spectral, morphological and thermal properties via FTIR, UV-visible, scanning electron microscopy (SEM) and thermogravimetric (TGA) analyses. Theoretical calculations were performed by using Gaussian 09 software via the DFT/B3LYP method with the 6-311G basis set. FTIR confirmed the formation of hydroquinone modified PTh when the polymerization was carried out by magnetic stirring and ultrasonication, while the formation of BQ modified PTh was obtained by microwave irradiation. The electronic transitions obtained via experimental UV-visible studies were also found to be in close agreement with the theoretical spectra. SEM revealed a well-formed morphology comprising needle shaped rods for the oligomer synthesized under microwave irradiation. The TGA-DTA studies revealed low char content for the above oligomer, while the florescence studies revealed intense emission around 450 nm. The highest quantum yield was found to be 0.024, which also showed high singlet oxygen generation tendency as well as a high single oxygen quantum yield of 0.30 and could be utilized to design imaging probes applicable in photodynamic therapy.