Surface heterogeneity of polysiloxane xerogels functionalized by 3-aminopropyl groups

DRIFT spectra of xerogels synthesized by co-condensation of tetraethoxysilane (or 1,2-bis(triethoxysilyl)ethane) and 3-aminopropyltriethoxysilane have been measured using termoevacuation in the temperature range 50-350 degrees C. The disappearance of bands related to the vibrations of water molecule with temperature growth and shifts of absorption band related to the deformation vibrations of amino groups to the high-frequency region have been observed. The formation of a new band in the range of 3650-3660 cm(-1) has been attributed to stretching vibrations of silanol groups. The simplest change of surface layer composition in the amino-containing xerogels by water removal results in transformation of one type of hydrogen bond to another. The first type is associated with forming of cyclical structure with participation of 3-aminopropyl and silanol groups and water molecule, [ Si(CH2)(3)H2NHO(H)center dot center dot center dot HOSi ], the other type is associated with the interaction of amino groups between each other. (C) 2010 Elsevier B.V. All rights reserved.