Synthesis and nonlinear properties of poly[1,4-bis(4-alkylpyridinium)butadiyne triflate]

1,4-Bis(4-alkylpyridinium)butadiyne triflate (2a and 2b) that was prepared by the reaction of 1,4-bis(4-pyridyl)butadiyne (1) with alkyl trifluoro-methanesulfonate, was found to grow into a large crystal as a result of the quaternized structure. The thermal treatment of 2a and 2b gave rise to 1,4-addition polymerization to yield the polydiacetylene. The third-order nonlinear optical susceptibility [X (3) ] of the polymer was determined by the femto-second Z-scan method to exhibit the remarkable high value of 1.1 × 10 -11 esu at 650 nm.