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

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 similar to 300 nm. From the cyclic voltammograms (CVs) recorded for the electrochemically polymerized SNS monomers the electrochemical gaps (similar to 1.3 eV) and HOMO and LUMO energies have been estimated. The UV-visible spectral analysis of polymers revealed electronic transitions corresponding to the pi-pi* transitions (optical gap of similar to 2 eV), and under gap ones in the range of 550-850 nm. FT-IR spectra reveal the coupling of a-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 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.