NMR linewidth, relaxation and diffusion studies of hexamethyldisilane confined in porous silica

✍ Scribed by Dagfinn W. Aksnes; Liudvikas Kimtys

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 253 KB
• Volume: 36
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(1998100)36:10<747::aid-omr388>3.0.co;2-#

✦ Synopsis

The rotational and translational dynamics of hexamethyldisilane conÐned within silica pores of diameter 4, 6 and 20 nm were studied as a function of temperature by measuring 1H and 13C NMR linewidths, self-di †usion coefficients, spinÈspin relaxation times and spinÈlattice relaxation times, and the results were compared with values obtained for the bulk material. The conÐnement in the pores gives rise to substantial changes in the molecular dynamics and phase behaviour. The lineshape, and self-di †usion measurements revealed a two-T 2 phase system consisting of a liquid-like component at the surface and a crystalline solid in the centre of the pore. The highly mobile surface layer is observable far below the reduced transition temperature of the conÐned hexamethyldisilane. A high di †usion rate of the adsorbed hexamethyldisilane is observed over a wide temperature range, even well below the region of the depressed transition point. The di †usion coefficient of the molecules in the surface layer is three orders of magnitude larger than in the plastic phase of bulk hexamethyldisilane.

1998 John Wiley & ( Sons, Ltd.