Thermoelastic and stress-optical behavior of aromatic-aliphatic polyester networks

Abstract

Thermoelastic networks were prepared by crosslinking hydroxyl terminated poly(pentamethylene glycol isophthalate) with tri(p-isocyanate-phenyl)-thiophosphate. The thermoelastic and stress-optical behavior of the networks were studied at several temperatures in the range of 10–70 °C. The values of the temperature coefficient of the unperturbed dimensions, d ln〈r2〉/dT, and the optical configuration parameter Δa were −4.5×10−3 K−1 and 22.7×10−24 cm3, respectively. Theoretical calculations carried out with the rotational isomeric state model gives values of d ln〈r2〉/dT in very good agreement with the experimental results. However, the theoretical values of Δa are nearly one order of magnitude lower than the experimental ones. No reasonable modification of conformational energies or contributions to the anisotropic part of the polarizability tensor would achieve agreement between theory and experiments. The discrepancy between theoretical and experimental results may be qualitatively explained by intermolecular interactions.