title: Investigation on conformational order and mobility of diamondbond-C18 and C18-alkyl modified silica gels by Fourier transform infrared and solid-state NMR spectroscopy.
abstract: The effect of surface coverage and solid supports on the conformational order of alkyl chains of commercially available carbon clad zirconia based supports and synthesised C18-alkyl modified silica based supports are probed in the dry state for the first time using variable temperature Fourier transform infrared (FT-IR) and solid-state 13C NMR spectroscopy. From FT-IR spectroscopy, the conformational order of alkyl chains tethered to the substrates is examined by the analysis of CH2 symmetric and anti-symmetric stretching bands. Through solid-state 13C NMR spectroscopy, the order is inferred from the relative intensity of the main methylene carbon resonance assigned to trans and trans-gauche conformations. It is found that molecules tethered to the graphite layer experience a strongly diamagnetic component of the highly anisotropic magnetic susceptibility of the graphite lattice, which reflects upfield shift in the 13C NMR spectra of commercially available octadecyl-modified carbon clad zirconia based column materials. The present results prove that temperature, surface coverage and solid supports have an influence on the conformational order and mobility of alkyl chains tethered to the carbon clad inorganic metal oxides.
authors.affiliation: Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
authors.forename: Gokulakrishnan
authors.initials: G
authors.lastname: Srinivasan
authors.forename: Angelos
authors.initials: A
authors.lastname: Kyrlidis
authors.forename: Clayton
authors.initials: C
authors.lastname: McNeff
authors.forename: Klaus
authors.initials: K
authors.lastname: Müller
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D015040:Zirconium / Q000737:chemistry*
chemical_list: D058428:Silica Gel; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide