Substituted oligothiophenes polymerization

The absorption edges of the broadband due to the n— n transition are red-shifted with increasing degrees of polymerization of the oligomers. The absorbance of the TZ—n band is increased suddenly when the degree of polymerization reaches six [174]. These are consistent with results by Fichou et al. [176] for non-substituted oligothiophenes. The extinction coefficient of the absorption maximum of about 10 cm for the hexamer (DMSxT) is comparable to that of polythiophenes. 

K. Waragai, H. Akimichi, S. Hotta, H. Kano and H. Sakaki, FET characteristics of substituted oligothiophenes with a series of polymerization degrees, Synth. Metal., 1993,57,4053. 

Huisman et al. studied the LC behavior of semiconducting oligothiophenes 2.53 (n = 4-8) (Chart 1.12), which were substituted by polymerizable acrylate groups [119]. By using these materials for the fabrication of OFETs, it was observed that the use of polymer films resulted in a decrease in mobility by a factor of 10 compared with transistors made from the bisacrylate monomer. For example, the charge carrier mobility of 2.53 (n = 6) after polymerization was 6 x 10 " cm V s compared with 4 x 10 cm V s before... 

Whereas alkylsulfanyl- [46, 55] or dialkylamino-substituted [49] thiophenes cannot be electropolymerized and yield only oligomers, oligothiophenes (n = 2-4) bearing methylsulfanyl (7) or pyrrolidine (8) groups at the outer -positions lead to polymers with a high degree of polymerization (Scheme 9.9) [48, 49, 56]. Note that the electropolymerization proceeds in the case of 3,3 -dialkylsulfanyl-2,2 -bithiophenes [57]... 

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