Molecular dynamics study in PU/PBDO anisotropic elastomers by proton NMR relaxometry

In this work we present a proton spin-lattice relaxation study of the molecular dynamics in an urethane/urea anisotropic elastomer film and in the two precursor pre-polymers, using conventional and fast field cycling NMR techniques. The precursor pre-polymers used were polypropylene oxide with three isocyanate terminal groups (PU) and polybutadiene diol (PBDO). The proton spin-lattice relaxation time T-1 dispersions were obtained at several different temperatures in the frequency range of 4 kHz to 100 MHz. The results show that while the molecular dynamics in the two precursor pre-polymers is well explained by the Rouse model, the solid elastomer film exhibits a relaxation dispersion where regions I, II and III of molten chain dynamics are clearly seen. The solid anisotropic elastomer film shows a molecular dynamical behaviour similar to other isotropic networks.