In Situ ESR/UV−vis−NIR and ATR-FTIR Spectroelectrochemical Studies on the p-Doping of Copolymers of 3-Methylthiophene and 3-Hexylthiophene

• Published in: The journal of physical chemistry. B 2009-02, Vol.113 (8), p.2310-2316
• Main Authors: Cházaro-Ruiz, Luis F, Kellenberger, Andrea, Dunsch, Lothar
• Format: Article
• Language: English
• Subjects: B: Macromolecules, Soft Matter
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp806810r

A combined spectroelectrochemical study by ESR/UV−vis−NIR as well as FTIR spectroscopy on the influence of the copolymer composition on the stabilization of charges upon electrochemical p-doping is presented. As compared to the parent homopolymers 3-hexylthiophene (3-HeTh) and 3-methylthiophene (3-MeTh) which seems to be irregular, FTIR studies of the copolymer of both monomers (copMeHeTh) point to a regioregular structure. The in situ ESR and UV−vis−NIR spectroelectrochemistry at higher doping levels of the polymeric materials proves bipolarons and polaron pairs as stable charged states in poly(3-hexylthiophene) as well as the copolymer copMeHeTh. During the p-doping of poly(3-methylthiophene) bipolarons are the dominating species at higher doping levels. It is demonstrated that only the simultaneous use of both the ESR and the UV−vis−NIR spectroscopy enables the differentiation of polarons (paramagnetic) and polaron pairs (diamagnetic) in a conducting polymer.