Random coil configurations of poly(diethylene glycol isophthalate). Capability of model network formation

Abstract

AbstractValues of the mean‐square dipole moment 〈μ2〉 of poly(diethylene glycol isophthalate) were determined as a function of temperature by means of dielectric experiments carried out on solutions of the polymer in benzene. The value of the dipole moment ratio 〈μ2〉/(nm2), where nm2 is the mean‐square dipole moment of the chains in the idealization that all of the skeletal bonds are freely jointed, is 0,697 at 30°C. Trifunctional model networks were prepared by endlinking hydroxyl‐terminated chains with an aromatic triisocyanate. From thermoleastic experiments performed on the networks over the temperature range 20–80°C, it was found that the value of the temperature coefficient of the unperturbed dimensions 103 d In 〈r2〉0/dT amounts to 1,05 ± 0,17 K−1. The dipole moments and the temperature coefficients of both the dipole moments and the unperturbed dimensions were critically interpreted in terms of the Ratational Isomeric State (RIS) model. Stress‐strain experiments were also performed at 70°C on swollen and unswollen networks. The analysis of the isotherms suggests that the chemical crosslinks are not sufficient to account for the high modulus exhibited by the networks.