1,4-Bis(4-benzylpyridinium)butadiyne triflate was aggregated in dimethylformamide and spontaneously converted into the 1,4-addition type of polydiacetylone. The polymerization took place in a dipolar aprotic solvent with a large dielectric constant that could enhance the aggregation of the ionic diacetylene salt through the electrostatic interaction. The molecular weight of the diacetylene was leveled off after 30 h at 80 degreesC to reach 1.5 x 10(4) (number-average molecular weight) that consisted of the 1,4-addition type of polydiacetylene similar to polydiacetylenes obtained in the conventional solid-state polymerization. Electron spin resonance spectra revealed that diradicals were generated at the earlier state aggregation to give rise to a solution polymerization. The UV spectra also suggested the presence of the activated aggregation associated with the polymerization as well as the eximer emission spectra.