Zirconium and Hafnium Twin Monomers for Mixed Oxides

The synthesis of Zr and Hf twin monomers of type [M(2-(OCH2C4H3O)-C-c)(4)(xHOCH(2)(c)C(4)H(3)O)] (3, M=Zr, x=0; 4, M=Hf, x=1) and M[(2-OCH2-C6H4O)(2)(2-HOCH2-C6H4OH)] (5, M=Zr; 6, M=Hf) by reacting M(OR)(4) (M=Zr, R=(C3H7)-C-n, 1; M=Hf, R=(C4H9)-C-n, 2) with 2-furylmethanol or 2-hydroxybenzyl alcohol is discussed. Complexes3-6 were homopolymerized under acidic conditions. Additionally, 5 and 6 were copolymerized with 2,2-spirobi[4H-1,3,2-benzodioxasiline] (SBS). Under acidic conditions SBS forms a phenolic resin/SiO2 nanostructured material. The resulting hybrid materials from the homopolymerization of 3-6 and the copolymerized materials from 5 and 6 were characterized by standard solid-state analytics. The inorganic lattice of the MO2 materials from the homopolymerized complexes3-6 and SiO2/MO2 from the copolymerization of 5 and 6 with SBS was obtained by air oxidation. The oxide materials were characterized by X-ray powder diffraction (XRPD) and energy-dispersive X-ray analysis, which proved their identity. The inner surface area was determined by N-2 adsorption/desorption studies, which revealed surface areas of 100m(2)g(-1) for MO2. The mixed oxides SiO2/MO2 were additionally investigated by differential scanning calorimetry and variable-temperature XRPD to study the thermal behavior. It was found that crystallization of tetragonal MO2 nanoparticles is characteristic within the SiO2 matrix, but higher sintering temperatures caused crystallization of the SiO2 lattice.