Interdomain Communicaton via Magnetic Spin Diffusion in a Microphase-Separated Polyurethane Elastomer
High-resolution carbon-13 solid state NMR spectroscopy is employed to monitor communication between the rigid and mobile domains in a polyether-polyurethane elastomer via proton magnetization transport. Results from thermal analysis and polarized optical microscopy indicate that the urethane-rich hard domains are semicrystalline and exhibit spherulitic growth that is somewhat disordered. Proton magnetization gradients are established via mobility differences between the two domains, and the ensuing spin-diffusion process is monitored via the carbon-13 nuclear manifold. Chemical structural differences between the two types of segments produce high-resolution 13C NMR signals that allow one to track interdomain communication. Magnetic spin-temperature equilibration between the two domains occurs on the 10–100 ms time scale. This is consistent with a finely dispersed array of hard and soft microphases. The polyurethane proton-spin-diffusion results are similar to those obtained for a variety of SURLYN™ and KRATON™ commercial phase-separated copolymers.
KeywordsHard Segment Dipolar Coupling Soft Segment Spin Diffusion Polyurethane Elastomer
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