Wolf-Dietrich Hunnius

Reactive groups on polymer coated electrodes, 7. New electrogenerated electroactive polythiophenes with different protected carboxyl groups

By the protection of the carboxyl group of 3-thiopheneacetic acid with differently substituted benzyl groups a series of new thiophene derivatives were synthesized. While 3-thiopheneacetic acid is not electropolymerizable, the new obtained monomers can be easily electrooxidized to form stable electroactive polymers. The electrochemical characterizations show that the substitution of the benzyl groups exerts little effect on the electropolymerization process and that the obtained polymers exhibit the typical properties of polythiophene derivatives, e. g., redox behavior and electrochromism. SEM studies show that all synthesized monomers possess a very good film formability and the resulting polymers exhibit a rather compact and homogeneous morphology on the Pt electrodes also containing scattered particles. Using p-nitrobenzyl-protected polymer as an illustrative example, it was demonstrated that the used protecting group can be easily split off in the solid state and the desired reactive carboxyl group can be produced on the polymer surface. Therefore, through the protection of the carboxyl group, the electropolymerization and the following removal of the protecting group, a new type of polymer matrix material with reactive carboxyl groups was simply prepared by using commercially available 3-thiopheneacetic acid monomer.

Reactive groups on polymer coated electrodes, 8. Novel conducting polymer interfaces produced by electrochemical copolymerization of functionalized thiophene activated esters with 3-methylthiophene

With the synthesis of two new functionalized thiophene activated esters and their electrocopolymerization with 3-methylthiophene, two types of redox active polymers have been prepared. FTIR studies of the resultant polymers reveal that both types of activated ester groups withstand the applied electrooxidative conditions and are correctly integrated into the corresponding polymers. The electrocopolymerization experiments show that the composition of the obtained polymers strongly depends on the ratio of the components in the reaction medium. With the increase of the ratios of pentafluorophenyl thiophene-3-acetate/3-methylthiophene or succinimido thiophene-3-acetate/3-methylthiophene, a higher concentration of functionalized thiophene units is incorporated into the polymer chains. The measurement of the conductivity on these polymeric films gave a value in the range of 10 -3 to 10 -2 S.cm -1 , which is comparable to that of the unsubstituted polythiophene and consistent with the conjugation grade suggested by electrochemical and UV-vis spectroscopic data. As expected, the pendant reactive ester groups on the electrode surfaces react rapidly with different amino compounds without loss of the electroactivity of the polymers. Therefore, these novel polymeric materials can be used as electrode interfaces for further functionalizations, especially for the immobilization of amines, peptides, and enzymes.

Reactive groups on polymer‐coated electrodes, 9. New electroactive polythiophenes with epoxy and cyclic carbonate groups

Two new functionalized thiophene derivatives bearing epoxy and carbonate groups were synthesized. The electrooxidative polymerization of both monomers led to stable electroactive polymers, while the functional groups remained unchanged during the polymerization process. Electrochemical and spectroscopic data of the resulting homopolymers reveal that these polymers possess an extended conjugated π-electron system comparable to unfunctionalized poly(3-alkylthiophene)s. Both monomers can also easily copolymerize with 3-methylthiophene to form the corresponding conducting copolymers. SEM photographs show that the obtained homopolymers and copolymers exhibit a very compact homogeneous morphology, indicating that the new thiophene monomers have good formability of polymer films. The measurement of electrical conductivity of these polymers by means of two-probe method gave values in the range of 10 2 to 10 -1 S . cm -1 . Using butylamine and 2-aminoanthraquinone as model compounds, it was demonstrated that amino compounds easily react with pendant epoxy and cyclic carbonate groups and are convalently attached to the new electroactive polymer surfaces. Thus, a new type of conducting polymers with pendant reactive groups was developed.