The opto-mechanical behaviour of a rigid diacetylene-containing segmented copolyurethane has been investigated in detail by using Raman spectroscopy. Experiments were carried out to determine the tensile and compressive strain dependence of the Raman frequency of the C drop C triple bond stretching mode in the copolymer. A similar initial strain-induced frequency shift of 4.7+/-0.5 cm(-1)/% strain was found in both tensile and compression tests. Angular strains were measured by obtaining the Raman spectra of the copolymer at different angles of the laser beam polarization with respect to the principal tensile axis, and it was found that the experimental results are in general agreement with classical elasticity theory, although they differ in detail. The molecular deformation of the polydiacetylene moieties in the copolymer has also been discussed.