Effects of the ethoxy and diethylamino substituent on the electrochemical and conducting properties of poly[(silanylene)oligothienylenes]

Polymers composed of alternating ethoxypropyl- or diethylaminohexylsilanylene and oligo(2,5-thienylene) units, [(SiRX)(C4H2S)m]n (3a–5a, R=Pr, X=OEt, m=3–5; 5b, R=Hex, X=Et2N, m=5) were synthesized and their properties were investigated in comparison with those of the diethylsilanylene analogs, [(SiEt2)(C4H2S)m]n (3c–5c, m=3–5). The UV and emission bands, and anodic peaks in cyclic voltammograms of polymers 3a–5a and 5b are at almost the same energies as those of the respective 3c–5c with the same number of m. However, polymers 3a–5a and 5b were found to be much more stable toward electrochemical oxidation and reduction, as compared with 3c–5c with the same number of m. Polymers 3a–5a became conducting upon doping with FeCl3 with the conductivities in the order of 10−2–10−1 S cm−1, similar to the diethylsilanylene analogs 3c–5c. In contrast, polymer 5b exhibited highly conducting properties when doped with I2, whose conductivity was determined to be 4.4 S cm−1. Photoconducting properties of polymer 4a and 4c are also described.