Nanocomposites based on nanosized inorganic particles and clusters represent an attractive field of research activity because of the possibility to tailor and optimize the properties of the resulting materials for various applications. In general, unmodified nano-particles tend to aggregate in the polymer matrix, resulting in poor properties. The decrease in size of the inorganic component into nano dimension and its incorporation in a polymer matrix, may result in novel materials with interesting properties Furthermore, the properties of the nanocomposites depend on the morphology of the inorganic phase, which has to be controlled over several length scales. Presently, Ti-oxo-clusters (figure 1a) functionalized with 8 methacrylate polymerizable groups have been introduced in a Dimethacryloxy-tetraethoxylated bisphenol-A matrix.

The resulting nanohybrids have been characterised with SAXS, TEM, DMTA and TGA. As seen in figure 2, the introduction of the nanoclusters has resulted in the formation of fractal like aggregates.

The presence of such fractal aggregates has resulted in a significant increase of stiffness especially below the Tg of the matrix. This can be seen in figure 3, where the elastic moduli of the hybrid nanomaterials and of the neat matrix are shown.

The nanohybrids exhibited also enhanced thermal stability with the incorporation of the Ti-oxo clusters as may be seen in figure 4.

Hydrogels have received considerable attention in the past due to their versatility and attractive properties. Our research group is interested in the preparation of magnetic hybrid hydrogels for targeted drug release applications. To achieve this aim hydrogels of PNIPAM-co- acrylic acid are synthesised and used as templates for the deposition of magnetic nanoparticles (fig. 5)

The magnetic nanoparticles consist of the maghemite phase of Fe₂O₃ and with careful control of the precipitation conditions raspberry morphologies may be obtained. The resulting composite hydrogels exhibit superparamagnetic behaviour as can be seen in figure 6.

The composite hydrogels exhibit an intriguing behaviour as they undergo a volume phase transition at 40 °C, temperature above the one of healthy human living tissue (36.6 °C) (fig. 7)

Systems consisting of organic polymer particles on which ceramic oxide nanoparticles have been deposited are interesting materials for use in a variety of applications (e.g. in photonic crystals, as nanoreactors, shielding applications, as means for controlled dispersion of nanoparticles in nanocomposites, etc.). Our group has a strong interest in the preparation and the characterisation of such materials. The general scheme used for the preparation of hybrid particles is depicted in figure 8.

Depending on the reaction conditions core-shell or raspberry morphologies may be obtained. The organic core used in our studies consists of PS copolymerised with acetoacetoxyethyl methacrylate (AAEM), which provides the necessary surface functionality for a controlled precipitation of the nanoparticles. Two systems have been so far investigated; the first based on ZnO and the second based on TiO₂. A very interesting aspect concerns the fact that the organic core may be removed either by dissolution or via calcination yielding hollow nanopsheres. Such materials are shown in figure 9 for the TiO₂ system.