INFRARED STUDY OF THE ADSORPTION OF 1-AMINOPROPYLTRIALKOXYSILANES ON SILICA AT THE SOLID/LIQUID INTERFACE

Infrared spectra are reported for silica in two states of surface hydroxylation immersed in carbon tetrachloride containing in particular (MeO)(3)SiCH2CH2CH2NH2. Adsorption involved hydrogen bonding between silanol and OMe or NH2 groups. At moderate coverages the silane was bonded to two or three silanol groups via OMe groups, but at high coverages reorientation in the adsorbed layer accompanied further adsorption, leading to 1:1 silanol:silane hydrogen bonding solely via amino groups. This behavior was unaffected by the degree of overall surface hydroxylation. Adjacent interacting surface silanol were more reluctant to be involved in bi- or tridentate bonding but at high silane concentrations also gave a 1:1 interaction via NH2 groups. (C) 1995 Academic Press, Inc.