Analysis of Poly(thiourethane) Covalent Adaptable Network through Broadband Dielectric Spectroscopy

The dielectric spectra of the poly(thiourethane) network, HDI-S3, have been analyzed to know the nature and the cooperativity of each of the six dielectric processes observed. At low temperatures, Y1, Y2, and fi dielectric relaxations were attributed to noncooperative local motions in the glassy state, in which apparent activation energies are 30, 36, and 60 kJ center dot mol-1, respectively. At higher temperatures, three dielectric relaxations are observed (alpha Tg, alpha*, p). The alpha Tg relaxation is attributed to the glass transition, and it is overlapped with the alpha* relaxation. The molecular origin of alpha* relaxation is associated with the bond exchange reaction. Finally, the p relaxation is ascribed to the heterogeneity of the sample although its origin is uncertain. The DC conductivity (sigma DC) is found to be an appropriate variable to analyze the bond exchange reaction. Accordingly, the HDI-S3 has a molecular exchange mechanism of dissociative nature.