Third generation of conducting polymers: Spectroelectrochemical investigations on viologen functionalized poly (3-alkylthiophenes)

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Abstract
Results of in situ electron spin resonance, optical absorption, and Fourier transform infrared spectroscopic studies during electrochemical doping and undoping processes of viologen functionalized poly (3‐alkylthiophenes) are reported. Effects of the functional group on the electronic properties of the polythiophene backbone in its conducting state are observed resulting in localization of the charge carriers. Radicals on the viologen side group show hyperfine structured electron spin resonance signals indicating a rapid motional averaging of anisotropic electron‐nuclear couplings. Experimental results are discussed by comparison with other substituted polythiophenes in terms of conformational effects of the acceptor group on the conducting polymer backbone. A structural model with counterion complexation between polythiophene backbone and the viologen functional unit is presented.