The influence of the chemical structure on the dielectric behavior of triazine derivative-based polyurethane–urea elastomers

摘要

Three series of linear and crosslinked polyurethane urea with heterocyclic triazine moieties in the main chain were synthesized and the films were prepared by casting and thermal curing. The molecular dynamics of the polyurethane urea have been studied by dielectric spectroscopy in the wide frequency range of 10~(0)–10~(6) Hz and in the temperature range of ?100 to 100?°C, by variation of the hard segments structure. Relaxation processes were observed in the dielectric spectra in proximity of the glass transition temperatures. All of the investigated samples showed two local relaxations (γ and β) and a primary relaxation (α), depending on the temperature and frequency range. For crosslinked samples, the α relaxation temperature increases with increasing the amount of crosslinkers. The dangling chains of castor oil (used as crosslinker) lead to the formation of imperfections in the network structure, affecting the relaxation process. It was found that inserting triazine derivatives in the hard segments modified dielectric behavior in comparison with linear chain extenders.