| Title
| - Electrochemical, Magnetic, and Electrical Properties of α,ω-Capped Sexithiophene Films. Part 3. Conduction in Poly(bis-terthienyl-B)s (B = Ethane, Disulfide, Diacetylene, Acetylene, Ethylene)
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| Abstract
| - Electrochemical oxidation of bis-terthienyl-B (B = ethane, disulfide, diacetylene, acetylene, ethylene) has been investigated. Monomers without and with 3,3′′-dialkylsubstitution are regularly coupled to polymers alternating sexithiophene and B moieties. The corresponding terthienyl homopolymers have also been produced for comparison. The polymers obtained are characterized by cyclic voltammetry, EQCM, UV−vis, and FTIR spectroscopy, in situ ESR and in situ conductivity. The conductivities of p-doped polymers with ethane or disulfide bridges fall in a narrow range (1−5 × 10−2 S cm−1) and are practically the same as those of α,ω-dimethylsexithiophene (1 × 10−2 S cm−1), suggesting that conduction proceeds without the help of the links via a direct redox hopping between sexithiophene blocks of adjacent polymer chains. In the cases of diacetylene and acetylene, conduction changes from redox to bipolaron-type but only in the case of ethylene the conductivity jumps to high values (1−5 S cm−1) corresponding to those of the polymers without the bridging moiety B, i.e., with shortened thiophene rings. DFT calculations of the bridge energy levels account for this result.
- Electrodeposited films of poly(bis-terthienyl-B) (B = ethane, disulfide, diacetylene, acetylene, ethylene) are investigated by CV, EQCM, in situ ESR, and in situ conductivity. The polymer p-conductivity is the same of α,ω-dimethylsexithiophene (1 × 10−2 S cm−1) suggesting direct hopping between sexithiophene blocks. Ethylene only shorts the blocks and conductivity jumps to the high values of polythiophenes (5 S cm−1).
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