New insight into microstructure-mediated segmental dynamics in select model poly(urethane urea) elastomers

Segmental dynamics in a series of 4,4′-dicyclohexylmethane diisocyanate-diethyltoluenediamine-poly(tetramethylene oxide) based poly(urethane urea) (PUU) elastomers have been investigated through a multi-scale characterization approach. This includes broadband dielectric analysis, solid-state nuclear magnetic resonance (NMR), plate impact, and impulsive stimulated scattering. Dielectric relaxation measurements applicable at frequencies up to 10⁶ Hz are useful for interpreting the high strain-rate deformation response; i.e. at the moment of target interaction with an accelerating impact or MHz stress wave excitation. Additionally, the capability of solid-state NMR to differentiate the microstructure-mediated segmental dynamics; correspondingly, the presence of a rigid phase (those in the phase-mixed regions) and a mobile phase associated with the soft-segment domains is demonstrated. These new insights not only further elucidate the microstructure details discerned through atomic force microscopy, but also enable the prediction of the macroscopically dynamic response in these model PUUs, particularly on the temporal scale over the range of μs-ns.