Bridged Polysilsequioxane Adsorption Materials Containing Phosphonic Acid Residues

I. V. Mel’nik^a, N. V. Stolyarchuk^a, O. A. Dudarko^a, Yu. L. Zub^a*,
A. Dabrowski^b, M. Barczak^b, and B. Alonso^c

^a Chuiko Institute of Surface Chemistry, Ukrainian National Academy of Sciences,
ul. Generala Naumova 17, Kiev 03164, Ukraine
^b Faculty of Chemistry, University of Maria Curie-Sklodowska, pl. M. Curie-Sklodowskiej 3, Lublin 20-031, Poland
^c Institute Charles Gerhardt - UMR 5253 (CNRS/ENSCM/UM2/UM1),
8 rue de I’Ecole Normale, 34296 Montpellier Cedex 5, France
*e-mail: Этот e-mail защищен от спам-ботов. Для его просмотра в вашем браузере должна быть включена поддержка Java-script

Received June 5, 2009

Abstract — Reactions of hydrolytic polycondensation of bis(triethoxysilane) [(C₂H₅O)₃Si]₂C₂H₄ (or
[(C₂H₅O)₃Si]₂C₆H₄) and functional agent (C₂H₅O)₃Si(CH₂)₂P(O)(OC₂H₅)₂ (alkoxysilanes molar ratio of 2: 1
and 4 : 1, fluoride ion catalyst and ethanol solvent) yielded powder-like xerogels that contained phosphonic acid
residues in the surface layer. Their treatment with boiling concentrated hydrochloric acid resulted in transfor-
mation of functional groups Si(CH₂)₂P(O)(OC₂H₅)₂ into acid groups Si(CH₂)₂P(O)(OH)₂. The methods of
IR, ¹H MAS NMRm and ¹³C, ²⁹Si, ³¹P MAS NMR spectroscopy showed the following (1) The surface layer in the initial xerogels contains not only phosphorus functional groups, but also some nonhydrolyzed ethoxysilyl groups as well as silanol groups. (2) The hydrochloric acid treatment of the initial xerogels causes the hydrolysis of not only ethoxy groups in the phosphonic acid residues, but also most residual ethoxysilyl groups. (3) Vacuum drying of xerogels after acid treatment forms Si(CH₂)₂P(O)(OH)–OSi links in their surface layer (not more than 20% of phosphorus-containing groups). (4) According to ²⁹Si CP MAS NMR spectroscopic data, boiling acid treatment relatively enriches the xerogel structure T² and T³ units and accounts for the higher rigidity of the hybrid framework. These units also account for retention of the porous structure in these xerogels over time, while most initial xerogels have porous structures that collapse in 12–18 months of storage. The acid-
treated xerogels were attributed to microporous adsorbents (having specific surface area of 620 to 760 m²/g). According to the AFM data, both initial and acid-treated xerogels contain almost spherical aggregates of the primary particles (globules).