A highly efficient method to introduce planarity and rigidity into a conjugated polymer backbone using a catalytic main-chain alteration to convert alkynes of PPE into annulated alkenes in PPV was developed. Post-polymn. cyclization provided a rare O-substitution of vinyl units of PPV and endowed products with greater planarity and rigidity, resulting in red-shifts in absorbance and fluorescence and defined vibrational features. We hope to extend this cyclization strategy to establish higher order of planarity for other conjugated polymer classes. [on SciFinder(R)]