981 ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 6, pp. 981 986. Pleiades Publishing, Inc., 2006. Original Russian Text I.V. Mel’nik, N.V. Stolyarchuk, Yu.L. Zub, A. Dabrowski, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 6, pp. 992 997. ORGANIC SYNTHESIS AND INDUSTRIAL ORGANIC CHEMISTRY Polysiloxane Xerogels Containing Arch-fixed Urea Groups I. V. Mel’nik, N. V. Stolyarchuk, Yu. L. Zub, and A. Dabrowski Institute of Surface Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine Maria Curie-Sklodowska University, Lublin, Poland Received February 21, 2006 Abstract A sol gel procedure was suggested for preparing polysiloxane xerogels containing arch-fixed urea groups. The presence of these groups was confirmed by IR spectroscopy. The surface layer of the xero- gels prepared exhibits enhanced hydrolytic stability in nonoxidizing acids. DOI: 10.1134/S1070427206060206 Functional materials based on silica are well known and are widely used in many areas, including chroma- tography, heterogeneous catalysis, and sorption proc- esses [1 4]. A frequently used method of their prep- aration involves modification of a surface with chloro or alkoxy derivatives of silicon, which allows for- mation of a surface layer with required properties. However, this method does not allow preparation of materials with a high and controllable content of func- tional groups. Furthermore, the hydrolytic and ther- mal stability of functional surface layers prepared by this method is, as a rule, relatively low. The low stab- ility may be caused by the fact that, with traditional modifiers (e.g., trifunctional silanes), a large amount of structural units of type Si(OR) 2 R (T 1 ) is formed (R = H or alkyl; R is a functional group being in- troduced) [5]. In this case, the functional group is linked to the matrix surface by a single siloxane bond, Si O Si(OR) 2 R, and the silicon atom bearing the functional group also contains alkoxy and/or si- lanol groups. An alternative pathway is based on the sol gel method; it allows one-step preparation of functional- ized polysiloxane xerogels [6, 7] containing mainly structural units of types =Si(OR)R (T 2 ) and SiR (T 3 ) on the surface. In addition, an increase in the number of spacers (hydrocarbon chains) linking the functional group with the surface of the polysiloxane framework and leading to formation of arch structures should also enhance the hydrolytic and thermal stability of the surface layer. The goal of this study was to develop sol gel procedures for preparing xerogels containing arch- fixed functional groups in the surface layer. As func- tional groups we chose urea groups, which are effi- cient in recovery and separation of rare-earth metal ions [8] and in preparation of membranes [9] and wear-resistant protective coatings on the surface of lenses made of organic polymers [10]. EXPERIMENTAL As starting compounds we used diethylenetriamine H 2 N(CH 2 ) 2 NH(CH 2 ) 2 NH 2 (DETA, Aldrich, 99%); 1,4,10-trioxa-7,13-diazacyclopentadecane (TDCPD, Aldrich, 99%); tetraethoxysilane Si(OC 2 H 5 ) 4 (TEOS, Aldrich, 98%); bis[3-(trimethoxysilyl)propyl]amine [(CH 3 O) 3 Si(CH 2 ) 3 ] 2 NH (BTMPA, Fluka, 97%); 3-isocyanatopropyltriethoxysilane (C 2 H 5 O) 3 Si(CH 2 ) 3 NCO (IPTES, Aldrich, 95%); NH 4 F (Fluka, 98%). Nonaqueous solvents (>99% pure) were dehydrated by the standard procedures. All the manipulations pre- ceding the sol gel syntheses were performed in a dry nitrogen flow, using the standard Schlenk technique. The elemental analysis was performed with a Carlo Erba EA 1108 analyzer. The IR spectra of the alkoxy- silanes were recorded on a Nicolet Nexus FTIR spec- trometer in the transmission mode (NaCl windows), and those of the xerogels, on a Thermo Nicolet Nexus FTIR spectrometer in the reflection mode (4000 400 cm 1 ); for this purpose, samples were ground with preliminarily calcined KBr in a 1 : 20 ratio. The 1 H NMR spectra were measured on a Bruker AC-300 spectrometer, using tetramethylsilane as reference. The mass spectra were taken on a Finnigan SSQ 710 mass spectrometer. The thermal analysis was per- formed with a Q-1500D in an air flow (temperature