Strain measurement in diacetylene-containing copolymers using Raman spectroscopy

Rigid diacetylene-containing block copolymers are shown to have Raman spectra similar to those of polydiacetylene single crystals. The vibrational frequencies of certain main-chain Raman-active modes of the copolymers are sensitive to deformation which enables strain measurement to be made by following the shift in the Raman band positions. Measurements of the stress concentrations around defects in copolymer specimens during deformation have been carried out using Raman spectroscopy and they have been compared with theoretical analyses of stress concentrations. There is good agreement between the theoretical and experimental measurements and it has been demonstrated that the use of Raman spectroscopy allows the measurement of stress or strain in complex situations for which no theoretical solutions exist.