Deuterium Nuclear Magnetic Resonance Studies of Alkyl Modified Silica

Article abstract of DOI:10.1021/j100349a027

Selectively deuterated n-alkyldimethylchlorosilanes were synthesized and used to prepare both chemically modified and physically coated porous silica. ²H NMR spectra were recorded on these modified solids at 46.1 MHz.A sharp liquidlike resonance was observed for the physically coated sample indicative of a complete averaging of the quadrupole interactions.Broad Lorentzian-shaped resonances were observed from all of the chemically modified surfaces with widths less than that expected for rigid-limit conditions.Similar line widths were observed for deuterons in the first and fourth positions and decreases in widths for deuterons toward the free end of the chain.The line shapes are ascribable to the presence of slow motions and the absence of a unique axis of reorientation.Spin-lattice relaxation times also were measured as a function of temperature for the chemically modified surfaces.These latter data as well as line width data indicate that there are at least two different motional domains.