Organo-metallic compounds of aluminum or iron as components of hybrid inorganic-organic materials

Inorganic-organic hybrid materials were prepared in one-step process by mixing Al(OBus)2(Etac) or Fe(acac)3 and 2-hydroxyethyl methacrylate (HEMA) with benzoyl peroxide (BPO) as polymerization initiator. Molar ratio HEMA/metal compound between 3 and 4 was used. The mixtures stiffened after mild thermal treatment at 80°C, producing monoliths. The material obtained from Al(OBus)2(Etac) is transparent and homogeneous, whereas that derived from Fe(acac)3 is opaque and dark red. Differential Scanning Calorimetric (DSC) and Thermo-Gravimetric and Mass Spectroscopic (TG-MS) analyses were performed in order to establish the nature and the extent of the chemical interaction between the organic and the inorganic components. With respect pure p-HEMA, the hybrids show modified and additional properties due to the presence of inorganic domains. These are generated in situ by hydrolysis and polycondensation when the aluminum precursor is used, whereas iron hybrid materials are mainly constituted of domains of Fe(acac)3, coordinated to poly-HEMA. The inorganic component of both the hybrid materials is supposed to be responsible for the weight changes recorded after the immersion in distilled water. Elastic modulus and strength of monoliths have been evaluated by four points bending test, whereas Dynamical Mechanical Thermal Analysis (DMTA) provided information on their behavior under heating. The aluminum-based hybrid is a brittle cross-linked material, even after a long time in water. On the other hand, the iron-based materials show a thermoplastic behavior and an interesting capacity of being shaped after heating or swelling in water.