DIRECT-DETECTION OF CONNECTIVITIES IN GLASSES BY 2D NMR

P-31 two-dimensional (2D) nuclear magnetic resonance (NMR) is proposed as a powerful tool for direct investigation of the connectivities between like or different Q(n) units in glasses or the medium-range order. The entire experiment was carried out under conditions of fast magic angle sample spinning (MAS). The magnetization transfer was obtained by recoupling of the dipole-dipole interaction despite the fast MAS. The mixing time dependence of the 2D spectra for a binary Na2O-P2O5 glass suggests an almost regular alternation of Q2 and Q3 units for that glass.