DFT and experimental infrared study on electrochemically synthesized poly(3-methylthiophene) (P3MT)

In this work we synthesized electrochemically the poly(3-methylthiophene) (P3MT), made infrared measures and DFT calculation of bond lengths, angles, dipole moment and harmonic vibrations of the 3-methylthiophene. For several 3-methylthiophene oligomers as dimers, trimers and quadrimers, we compare the calculated harmonic vibrations and the experimental infrared spectrum of P3MT to verify the presence of these species on the polymeric material obtained by electrochemical synthesis. The DFT calculations of the 3-methylthiophene using B3PW91 hybrid functional and 6-311++G** basis set provided good correspondence with experimental data which credits the results of this method in the calculation for the short oligomers and the study of IR spectra proposed in this paper. The predicted spectra for the oligomers indicated that the sample synthesized by electrochemistry has monomer its constitution, as well as trimers, quadrimers, HH and HT dimers, but not detectable TT dimers.

► Poly(3-methylthiophene) was electrochemically synthesized and measured FTIR spectrum.
► 3-Methylthiophene molecular properties were calculated using DFT/B3PW91 method.
► Good agreement with molecular experimental data credits the DFT results for IR study.
► Predicted spectra point that electrochemical synthesized sample has monomers in it.
► Predicted spectra indicate not detectable TT dimers in the sample.