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Trabelsi, S. ; Janke, A. ; Häßler, R. ; Zafeiropoulos, N.E. ; Fornasieri, G. ; Bocchini, S. ; Rozes, L. ; Stamm, M. ; Gérard, J.-F. ; Sanchez, C.
Novel Organo-Functional Titanium-oxo-cluster-Based Hybrid Materials with Enhanced Thermomechanical and Thermal Properties

Two novel nanomaterials based on hybrid organic-inorganic polymers have been preparedvia free radical polymerization of (I) dimethacrylate oligomers and (II) 2-hydroxyethyl methacrylate(HEMA) in the presence of different contents of organically modified titanium-oxo-clusters Ti16O16(OEt)24(OC2H4Mc)8 (OMc = methacrylate). Investigations, combining small-angle X-ray scattering (SAXS),transmission electron microscopy (TEM), and energy-filtering transmission electron microscopy (EFTEM)lead to consistent structural and morphological characteristics for both grades of hybrid materials.Structural features, such as the subunit size and fractal dimensions are extracted from SAX
S profiles.For the first grade of nanomaterials, i.e., for different content of titanium-oxo-clusters (2.5, 5 and 7.5 wt%) incorporated into a dimethacrylate-based matrix, aggregates with ramified mass fractal structureswere found. Semiquantitative studies of TEM and EFTEM images revealed the presence of a uniformsize distribution in the case of 2.5 wt % titanium cluster content with a typical size of 30 nm. A largersize distribution has been found for the 5 wt % and 7.5 wt % between 30 and 180 nm. For the secondgrade of nanomaterials, i.e., the 19.2 wt % of organically modified titanium clusters incorporated intopoly(HEMA), compact and highly dense aggregates with a size distribution from a few nm up to 50 nmwere found from TEM and EFTEM images. A significant increase of the storage modulus for the firstgrade of nanomaterials was revealed by dynamic mechanical analysis (DMA). The incorporation of Tinanoclusters in the matrix lead to a significant alteration of the system's hardness as indicated throughnano-indentation measurements. Thermogravimetric analysis also indicated a significant enhancementof the thermal stability compared to the neat matrix, probably because of the antioxidant effect of thetitanium-oxo-clusters.

Macromolecules 38



Erschienen am
August 2005


Nanostructured Materials