Polydiphenylacetylene (PDPA) derivaitves consisting of different central atoms of C, Si, and Ge in the pendent group were comparatively investigated in normal, swollen, and acid-treated states. The Ge-containing PDPA was more emissive than the other two both in solution and in solid states. All the polymers showed emission enhancement in a swollen state: The PL quantum yields increased remarkably when swollen in an appropriate non-solvent. The Si and Ge atoms were easily removed from the polymer chain under acidic condition, as a result, the PL intensity was significantly decreased and the polymers turned to be insoluble in common organic solvents. Although the tert-butyl group of C-containing PDPA remained intact during the acid exposure, similar PL attenuation occurred.