XRD and NMR characterization of synthetic hectorites and the corresponding surfactant-exchanged clays

Synthetic hectorites and the corresponding surfactant-exchanged clays have been characterized by X-ray diffraction and (super 1) H, (super 7) Li, (super 13) C, (super 23) Na and (super 29) Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The low-charge clays retain water more efficiently, forming aggregates without extensive drying. The hydroxylated hectorite exhibits two (super 1) H NMR signals near 0 ppm whereas the fluorohectorites are characterized by a single peak in the same region. The (super 23) Na 2D 3Q magic angle spinning (MAS) spectra of the low-charge hectorites show a single peak. The (super 29) Si NMR shift depends on the interlayer charge. Tactoids formed by the low-charge hectorites reduce the rate of surfactant incorporation. The population of the all-trans conformer of the hydrocarbon chain, determined by (super 13) C MASNMR, varies with the surfactant content. (super 13) C NMR relaxation data show an increase in mobility with the surfactant loading and along the long alkyl chain, from the polar head to the terminal group. Complexity of the motional behaviour precludes any detailed analysis. These modified clays are not useful in preparing poly(epsilon -caprolactone) nanocomposites by in situ polymerization.