New π-conjugated polyelectrolyte composed of alkylphenoxathiinium-type repeating units

The polymer-analogous condensation of aryl sulfoxides was employed as a convenient method to prepare the ladder-type polymer containing λ-alkylsulfanyliumdiyl linkages in the backbone that force the consecutive aromatic rings into planarity. The bridging λ-alkylsulfanyliumdiyl groups allowed for the electron delocalization between the aromatic subunits to give the π-conjugated system, which was suggested by the film properties and supported by the MO calculations. The reduction of the band gap from that of poly(alkylsulfonio-1,4-phenylene) was attributed to an increase in the planarity of the molecular geometry, which stabilized the LUMO through the symmetry-allowed bonding interaction between the p_z orbitals of the sulfur atom and those of the adjacent carbon atoms.