Details

Autor(en) / Beteiligte

• Mel’nik, I. V.
• Stolyarchuk, N. V.
• Dudarko, O. A.
• Zub, Yu. L.
• Dabrowski, A.
• Barczak, M.
• Alonso, B.

Titel

Bridged polysilsequioxane adsorption materials containing phosphonic acid residues

Ist Teil von

• Protection of metals and physical chemistry of surfaces, 2010-03, Vol.46 (2), p.206-214

Ort / Verlag

Dordrecht: SP MAIK Nauka/Interperiodica

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Reactions of hydrolytic polycondensation of bis(triethoxysilane) [(C 2 H 5 O) 3 Si] 2 C 2 H 4 (or [(C 2 H 5 O) 3 Si] 2 C 6 H 4 ) and functional agent (C 2 H 5 O) 3 Si(CH 2 ) 2 P(O)(OC 2 H 5 ) 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 transformation of functional groups ≡Si(CH 2 ) 2 P(O)(OC 2 H 5 ) 2 into acid groups ≡Si(CH 2 ) 2 P(O)(OH) 2 . The methods of IR, 1 H MAS NMRm and 13 C, 29 Si, 31 P MAS NMR spectroscopy showed the following (1) The surface layer in the initial xerogels contains not only phosphorus functional groups, but also some non-hydrolyzed 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(CH 2 ) 2 P(O)(OH)-OSi≡ links in their surface layer (not more than 20% of phosphorus-containing groups). (4) According to 29 Si CP MAS NMR spectroscopic data, boiling acid treatment relatively enriches the xerogel structure T 2 and T 3 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 m 2 /g). According to the AFM data, both initial and acid-treated xerogels contain almost spherical aggregates of the primary particles (globules).