Deuteron double-quantum NMR imaging of molecular order and mobility in solid polymers

Abstract

A novel solid-state deuteron NMR method for spectroscopic imaging is presented. It employs information about molecular orientation and dynamics obtained from broad ²H-NMR lineshapes governed by the anisotropic quadrupole interaction without sacrificing spatial resolution. To this end, double-quantum coherence is created, which is independent of the strength of the quadrupole coupling. In a Fourier-imaging scheme magnetic-field gradients are applied for spatial encoding during the evolution of double-quantum coherence. In the detection period single-quantum coherence is recorded, providing a spectroscopic dimension with a wide-line spectrum. Its lineshape contains spatially resolved information about molecular orientation and dynamics. Experimental results are presented for orientation imaging of drawn polyethylene and molecular-dynamics imaging in a composite sample of glassy polystyrene and glassy polycarbonate, where the two species can be discriminated based on both the NMR lineshape and the spin-lattice relaxation time T ₁.