Both cis- and trans-rich poly[p-(trimethylsilyl)phenylacetylene]s (PTM-SPAs) were synthesized using [Rh(norbornadiene)Cl](2)-TEA (TEA: triethylamine) and WCl6-Ph4Sn as catalysts, respectively. The Rh-based cis-rich polymer exhibited a remarkable fluorescence (FL) emission enhancement after thermal annealing (heating at 200 degrees C in N-2 atmosphere for 1 min), while the pristine polymer was almost entirely non-emissive. NMR and Raman spectroscopic studies clarified the occurrence of irreversible cis-trans isomerization under thermal annealing and suggested that the FL emission increased with an increase in the trans content of PTMSPA. Computer simulations of 12-mer model compounds clarified that the FL emission is a result of intramolecular excimers formed from side-on -stacking of phenyl groups, which is possible only along the backbone of the trans-based polymer.