Postpolymerization Grafting of Aniline Tetramer on Polythiophene Chain: Structural Organization of the Product and Its Electrochemical and Spectroelectrochemical Properties

We describe the preparation of solution-processible hybrid polymers, consisting of a polythiophene main chain and randomly distributed alkyl and oligoaniline side groups. The proposed procedure involves three steps: copolymerization of alkyl- and ester-group-substituted thiophenes to give the precursor polymer, followed by the hydrolysis of the pendant ester groups and aniline tetramer grafting through an amidation reaction. The proposed method is more versatile than previously used copolymerization procedures because higher tetraaniline grafting levels can be obtained. The postfunctionalized polymer is electrochemically active both in its oligoaniline part and in its conjugated polythiophene main chain. As shown by complementary voltammeric and UV−vis−NIR and Raman spectroelectrochemical studies, the polymer can be electrochemically doped selectively in its side oligoaniline chains or globally in the main chain as well as in the side chains. Selective side-chain doping can also be achieved chemically through protonation of the grafted oligoaniline groups in their semi-oxidized state. Doping with FeCl 3 is global and involves the oxidation of the main chain and Lewis acid complexation of the side chains, as shown by Mössbauer spectroscopy.