Poly(3‐dodecyl‐2,5‐thiophenediyl), a soluble and conducting polythiophene

Poly(3‐dodecyl‐2,5‐thiophenediyl)(PDDT) films were prepared by means of electrochemical polymerization of 3‐dodecylthiophene. PDDT is soluble in benzene, chloroform and tetrahydronaphthalene, and oxidized PDDT is soluble in tetrahydronaphthalene. The degree of polymerization was found to be 90 and the conductivity of an as‐grown film, containing hexafluorophosphate anion, is 67 S/cm. While the cyclic voltammograms of an as‐grown film have two anodic peaks and two cathodic peaks, those of a film cast from an oxidized polymer solution has one anodic peak and one cathodic peak. Two peaks would correspond to two conjugation length. Oxidized PDDT is partly soluble in chloroform, retaining oxidized states. UV‐near infrared spectra in solution were compared with those in a solid film. The energy of the interband transition was found to be much higher in the solution than in the film. The results indicate a rigid oxidized part and a flexible neutral part in the polymer chain. The concentration dependence of the spectra indicates that oxidized PDDT does not aggregate in solution.