The strong reduction of interchain interaction in poly-(2,5-dialkoxy-1,4-phenylenevinylene) films with a 2,5 O-(CH2)(12)-O closed chain substitution (bridged PPV), engineered to reduce the molecular packing in the solid state, is reported. Evidence of this effect unambiguously stems from the systematic comparison between the optical properties of a series of dialkoxy-PPV derivatives with bridged and open chain side groups. Reduction of interchain energy relaxation channels explains the close similarity between the optical spectra of bridged-PPV films and solutions, the higher photoluminescence efficiency and the lower threshold for the observation of spectral line narrowing in the solid state. (C) 1999 American Institute of Physics. [S0003- 6951(99)04840-8].