POLARIZATION TRANSFER ACROSS INTERFACES .1. SI-29 CROSS-POLARIZATION DYNAMICS AT THE POLY(VINYL ALCOHOL)-SILICA SOL-GEL INTERFACE

We discuss polarization transfer across interfaces as a family of solid-state NMR techniques for observing selectively the NMR spectra of surface and near-surface species. We apply one such technique to estimate the proximity of the backbone of poly(vinyl alcohol) (PVOH) to the surface of silica polymerized in situ through the acid-catalyzed sol-gel condensation of tetraethoxysilane (TEOS). Cross-polarization times measured in protonated, and selectively deuterated samples, can be analyzed semiquantitatively to yield approximate distance ratio information between the silica surface and the polymer backbone vs the hydroxyl groups. The distance ratio information will serve as an initial constraint for modeling the PVOH-silica interface using molecular dynamics calculations.