Preparation and use of diacetylene-containing polyesters for studying deformation micromechanics in model polyester-polyolefin blends

A range of diacetylene-containing polyesters have been prepared by polycondensation of terephthaloyl chloride with diacetylene diols of structure HO—(CH₂)_n—C≡C—C≡C—(CH₂)_n—OH, where n = 1, 2, 3, 4 and 9. The results from characterization of the polyesters by DSC and Raman spectroscopy are presented. The polyesters from the diols with n = 3 and n = 9 have melting points (T_m) of 186 and 88 °C, respectively, and cross-polymerise under irradiation, but not thermally. These polyesters were blended with isotactic polypropylene (T_m = 167 °C) and the blends compression-moulded into dumbbell specimens, which then were exposed to ⁶⁰Co γ-radiation to effect cross-polymerization of the polyester phases. The dumbbell specimens were subjected to simultaneous tensile testing and resonance Raman spectroscopy, and the shift in wavenumber of the C≡C stretching band of the polydiacetylene crosslinks used to determine the local stress in the polyester phases independent of the overall applied stress, thereby facilitating determination of the efficiency of stress transfer in the blends.