Alkyl Monolayers Research Articles

Alkyl monolayers covalently bonded to silicon surfaces

Alkyl monolayers covalently bonded to silicon surfaces

Physicochemical characterization of covalently bonded alkyl monolayers on silica surfaces

The physicochemical properties of silica surfaces covalently bonded with alkyl monolayers, in a chain length range from C 6 to C 22, are investigated by using chromatographic, ellipsometric and capacitance measurements. A compact structure is found with an interchain distance of about 0.67 nm; the experimental thickness is very close to the theoretical chain length value. The hydrophobic character of such chemically modified silica surfaces increases with the chain length.

Irreversible and reversible phase transitions of alkyl monolayers. Gas chromatographic evidence of polar solvent influence on the adsorbing properties of the layer

Further to Gilpin's observations in liquid chromatography of the irreversible transformation of alkyl grafts, following the replacement of an organic mobile phase by an aqueous one, we describe some gas chromatographic experiments which lead to similar (log Vs, I/T) plots, as a consequence of the same solvent release process. We use paraffin films on siliceous supports or hydroxylated liquid substrates or C22-alkyl bonded silica. These experiments demonstrate that this irreversible transition and the melting-like reversible transition are completely different phenomena. They confirm the existence of at least three kinds of monomeric alkyl films.