Influence of solvents on the conformational order of C18 alkyl modified silica gels

The influence of solvents on the conformational order of C18 alkyl modified silica gels is studied by means of variable temperature FTIR spectroscopy. Symmetric and anti-symmetric CH2 stretching modes were utilized for getting qualitative information about the changes in alkyl chain conformational order as a function of both protonated and perdeuterated solvents. It was found that interaction between the C18 alkyl modified silica gels and the mobile phase results in pronounced changes of the alkyl chain conformational order. Furthermore, it was observed that some perdeuterated solvents exhibit isotope effects, which again is reflected by a different alkyl chain conformational order as compared to the corresponding stationary phases with protonated solvents.