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 (1-5x10-2 S cm-1) and are practically the same of a,w-dimethylsexithiophene (1x10-2 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 shorted thiophene rings. DFT calculations of the bridge energy levels account for this result.
Electrochemical, magnetic, and electrical properties of a-w-capped sexithiophene film. Part 3. Conduction in poly(bis-terthienyl-B) (B = ethane, disulfide, diacetylene, ethylene)
Zotti G;Vercelli B;Berlin A;Destri S;
2008
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 (1-5x10-2 S cm-1) and are practically the same of a,w-dimethylsexithiophene (1x10-2 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 shorted thiophene rings. DFT calculations of the bridge energy levels account for this result.File | Dimensione | Formato | |
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