The opto-mechanical behaviour of diacetylene-containing segmented block copolymers

The effects of mechanical deformation on the optical properties of segmented copolyurethanes have been studied using resonance Raman spectroscopy. Linear elastomeric and glassy copolyurethanes, each containing diacetylene-urethane (DA-U) hard segment domains dispersed in a continuous polyether-urethane (PE-U) matrix, were prepared in bulk and themally cross-polymerised in the solid state. The crosslinked copolymers produced intense Raman spectra in which the {Mathematical expression} triple bond stretching Raman band at ∼2080 cm^-1 is well defined and shifts to lower frequency under the application of tensile stress. Shifts in Raman spectra have been used to monitor stress concentrations around defects such as holes and notches machined into copolyurethane sheets. The copolyurethanes are readily applied as surface coatings to various subtrates, and their use as optically stress/strain-sensitive materials (optical strain sensors) is demonstrated.