Abstract
The absorption and emission properties of excitons are investigated in a pure “red” phase of luminescent polydiacetylene wires. The values of the binding energy (Eb = 0.556 eV) and Bohr radius (r ~ 14 Å) make the “red” exciton similar to the one of the extensively studied “blue” phase, so the conformational modifications which lead to a reordering of excited states and luminescent emission do not strongly affect the exciton structure. The opening of a thermally activated non radiative channel leads to an efficient quenching of the intense luminescence observed at low temperature.