π-conjugated columnar polyacetylenes prepared with Rh complex catalysts

Highly stereospecific polymerization of monosubstituted acetylenes was carried out using the Rh complex, [Rh(norbornadiene)Cl]2 catalysts. The resulting polyacetylenes were characterized in detail by 1HNMR, ESR, laser Raman, diffuse reflective UV, and wide angle X‐ray diffraction methods. The data showed that the Rh complex were the preferred catalyst to selectively yield the corresponding cis‐transoid polymers even at room temperature when alcohol, triethylamine or water was used as the polymerization solvent. Additionally, the resulting cis polyacetylenes were found to have a helical form whose polymer is amorphous or composed of pseudohexagonal structures called π‐conjugated columnar as self‐assembly or super structure. Further compression of the amorphous cis polymers resulted in cis to trans isomerization at room temperature under vacuum, breaking rotationally the cis C=C bonds giving π‐radicals called solitons as the origin of a polymer magnet. On the other hand, the π‐conjugated columnar was also found to show an extremely longer wavelength absorption compared with that of the amorphous one, although the absorption maximum was shifted to a shorter wavelength when the columnar was destroyed by the compression. Therefore, the formation of the π‐conjugated columnar can be considered as a new and quite useful control method concerning color of such conjugated polymers, i.e., a new concept concerning the color of conjugated polymers.