Synthesis and properties of poly(N-benzoyl-2-ethynylpyridinium chloride)

A new ionic polyacetylene with N-benzoylpyridinium substituent was prepared by the activation polymerization of 2-ethynylpyridine by using benzoyl chloride without any additional initiator or catalyst. This reaction proceeded well in homogeneous manner to give a high yield of the polymer (yield: 89%). The initial light-brown solution of 2-ethynylpyridine and benzoyl chloride became a viscous dark-red solution as the polymerization proceeded. The activated acetylenic triple bond of N-benzoyl-2-ethynylpyridinium chloride, formed at first quaternarization process, was susceptible to linear polymerization. This polymer was completely soluble in water, methanol, DMF, and DMSO, and the polymer was found to be mostly amorphous. The instrumental analysis data on the polymer structure revealed that the polymer has conjugated polyene backbone structure with the designed N-benzoylpyridinium substituent. The photoluminescence peak is located at 509 nm corresponding to a photon energy of 2.44 eV. The electrochemical properties of this ionic polyacetylene were also measured and discussed.