Synthesis and Characterization of a Water-Soluble Ionic Polyacetylene Derivative

A new water-soluble ionic polyacetylene was synthesized by the acid-catalyzed polymerization of 2-ethynylpyridine using acrylic acid. The polymerization proceeded well to give a high yield of polymer. The acetylenic C ≡ C bond stretching (2110 cm¯¹) and acetylenic ≡ C-H bond stretching (3293 cm¯¹) peaks of 2-ethynylpyridine monomer were not seen in the FT-IR spectrum of polymer. The electro-optical and electrical properties of the ionic polyacetylene were measured and discussed. The resulting polymer showed strong maximum at 513 nm in the UV-Visible absorption, which is corresponding to photon energy of 2.42 eV. The energy gap width of polymer was estimated to be of 2.08 eV. It was observed that the electrochemical process of polymer is reproducible in the potential range of -1.80 to 1.60 V vs Ag/AgNO₃. HOMO and LUMO levels of polymer were 4.85 eV and 2.77 eV, respectively.