Selective CaCO3 Formation within Hydrogels

摘要

Nature materials with remarkable mechanical properties are often hybrid materials build-on common inorganic salts and a polymer component, like proteins or polysaccharides. Although all ingredients are accessible, the artificial reconstruction of such materials has not been yet succeeded, because defined nanostructures of the natural materials are responsible for their outstanding performance. Nacre is one of those natural CaCO3 composite materials that contain hierarchically ordered metastable crystals, which are responsible for its excellent mechanical properties. Finding the key factors of the nacre-formation and transferring it to an easy accomplishable, artificial system is the way to open this class of materials for technical applications. In order to create nacre-like structures several groups used surface mineralization in a layer-by-layer fashion. These methods often lead to structures close to the natural idol. Unfortunately they are elaborate, which makes it unlikely to obtain materials thicker than several micrometers. To receive access on artificial large-scale biomaterials it seems to be necessary to effectively calcify the bulk of pre-produced polymer networks. While the influences of low-molecular additives and polymers on crystallization of CaCO3 in solution and on surfaces are pretty well investigated, the understanding of the complex growth inside a polymer network is far more complicated. Thereby the interaction of the crystals with the polymer as well as the suppressed convection and the slowed diffusion of reactants play an important role. These limitations usually result in complex, non-classical and kinetic-controlled crystal growth that affords complex morphologies. Corresponding to this, structure and habit of the grown crystals in a polymer matrix can be influenced by changing gels density and composition, temperature of mineralization or concentration of the reactants. Different kinds of natural and synthetic matrix polymers are suitable to grow CaCO3 crystals within.