C-13 NUCLEAR-MAGNETIC-RESONANCE STUDIES OF CELLULOSE ESTER DERIVATIVES IN SOLUTION, POWDER AND MEMBRANES

A C-13 nuclear magnetic resonance study (with cross polarization and m agic angle spinning) is presented of commercially available cellulose acetate and cellulose propionate as powder samples and also in differe nt membranes. Some physical properties of the films are interpreted in the light of data obtained for the principal components of the shield ing tenser of C-13 nuclei on carbonyl groups. In particular, it is sho wn that the shielding asymmetry factor, measured on samples with a reg ular shape and with a fixed orientation in the rotor, is a sensitive p robe to ordered domains in the polymers.