Synthesis of poly-[2,5-di(thiophen-2-yl)-1H-pyrrole] derivatives and the effects of the substituents on their properties

•Three new polymers based on 2,5-di(thiophene-2-yl)-1H-pyrroles (SNS) have been synthesized.•The properties of the polymer are correlated with substituents attached to their structures.•The electrical conductivity of the polymers is fair and thermally activated.•The conductance of the polymers changes under humidity and ammonia exposure.

A series of conducting polymers based on 2,5-di(thiophen-2-yl)-1H-pyrrole (SNS) were synthesized by chemical and electrochemical polymerization of 1-(2-methoxyphenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole 1, 2,5-di(thiophen-2-yl)-1-(o-tolyl)-1H-pyrrole 2 and 1-(2-(2,5-di(thiophen-2-yl)1H-pyrrol-1-yl)phenyl)ethanone 3. The maximum of the UV–visible absorption bands of SNS monomers 1–3 occurred at ∼300 nm. From the cyclic voltammograms (CVs) recorded for the electrochemically polymerized SNS monomers the electrochemical gaps (∼1.3 eV) and HOMO and LUMO energies have been estimated. The UV–visible spectral analysis of polymers revealed electronic transitions corresponding to the π–π* transitions (optical gap of ∼2 eV), and under gap ones in the range of 550–850 nm. FT-IR spectra reveal the coupling of α-H of external thiophene rings during polymerization. The polymers having N-substituted benzene ring with electron donating substituents showed higher electrical conductivity than those with electron withdrawing substituents. The polymers exhibited good thermal stability up to 400 °C (less than 10% loss). The influence of the temperature, humidity and ammonia on the electrical conductivity of the polymers (pressed as pellets) has been also evaluated.