A phenylacetylene monomer, 4-(decyloxycarbonyl)phenylacetylene (DecCPA), was synthesized and polymerized using the combined catalyst system, i.e. [Rh(norbomadiene)Cl](2) and triethylamine, to give a yellow solid pi -conjugated polymer [poly(DecCPA)] of high molecular weight and cis-transoidal stereo-regular main chain. Poly(DecCPA) was measured using the total internal reflection fluorescence microscopy, which is a single molecule detection technique that is carried out in a tetrahydrofuran solution at room temperature with the light-twinkling of a single molecule being observed. This twinkling is a dynamic photon emission phenomenon of single poly(DecCPA) molecule that we mention specifically as a resultant from the time scale - changing very slowly in the time scale of milliseconds and seconds - with the changed fluorescent intensity being associated with the changing single polymer molecule conformation caused by the micro-Brownian motion. Although molecular dynamics was of the picosecond time scale, generally, this poly(DecCPA) molecule had the mode of the molecular motion of pi -conjugated main chain. This was very slow in the second time scale as was shown.