Molecular dynamics of linear and hyperbranched polyurethanes and their blends

The molecular dynamics of two polyurethanes with different architecture (linear and hyperbranched) and their blends with compositions 80/20 and 65/35 have been studied by dielectric spectroscopy and dynamic mechanical analysis yielding results complementary to those obtained by differential scanning calorimetry. In pure polyurethanes, relaxation phenomena correlated with glass transitions and with local chain motions are observed. The molecular dynamics in the blends is dominated by the linear component. A significant influence of hyperbranched polyurethane in the blends is observed only in the case of the primary relaxation connected with the high-temperature glass transition. At higher temperatures the dielectric spectra are dominated by conductivity.