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In Nature living organisms use a wide range of organic-inorganic hybrid materials, which are generally molded into specifically designed devices with fascinating properties. The structure, size, shape, orientation, texture, and assembly of the constituents of these materials are precisely controlled. The purpose of biomineralization is the study on biologically produced materials, such as shells, bones, and teeth, and the processes that lead to the formation of hierarchically structured composites. It is evident that the understanding and ultimately mimicking of the processes involved in biomineralization may provide new approaches to the fabrication of specialized organic-inorganic hybrid materials. Calcium carbonate is not only the most abundant in natural biominerals, but also a material of considerable industrial interest, and the study of the factors that affects its formation has a long history. Consequently, many researchers have engaged in unraveling the mysteries of calcium carbonate biomineralization. In the nature, the organisms fabricate inorganic single crystals with occluded proteins and polysaccharides, resulting in the biominerals with improved mechanical properties[1]. During the fabrication process, organic components, utilized based on their solubility properties, are believed to regulate the crystal nucleation and growth, modulate the crystal shape and size, and control the organization of nanoscale building blocks into complex structures. Many soluble organic additives such as surfactants, biomolecules, and double hydrophilic block copolymers (DHBCs) have been implemented into in vitro synthesis[2]. Such efforts mentioned above are mainly focused on the influence of organic functional groups, including the hydroxyl group, carboxyl group, amino group, phosphate, sulfates, and so on. Generally, it is believed that the regulation of organic components on crystals is attributed to their adsorptions onto crystals by the functional groups. But in real bio-systems, the mineralization processes occur in specific environment, usually at the interface between insoluble organic matrix and the aqueous solution. However, very little effort has been made to investigate the roles played by the insoluble matrix without any functional groups in the development of highly ordered hierarchical materials[3]. In this thesis, therefore, in the presence of an insoluble matrix, isotactic polypropylene (iPP) fibre, polyethylene fibres, nylon fibres and metal grid. It is important to point out that insoluble matrix played a unneglectful role. On the other hand, we conducted calcium carbonate crystallization experiments with soluble organic matrix such as PSS (poly(sodium p-styrenesulfonate)), citrate, PNMP-b-PMAA (poly[N-(2-methacryloyloxyethyl)pyrrolidone-b-poly(methylacylic acid), which is a novel kind of thermo-responsive polymer, in order to investigate the role of soluble organic matrix in the biomineralization. Morphological characterization of the polymorphs was done using scanning electron microscope (SEM) and transmission electron microscope (TEM), and the nature of the crystal lattice was identified using FTIR spectroscopy, selected area electron diffraction (SAED), and powder X-ray diffraction studies. On the basis of these results, a possible mechanism for the nucleation of CaCO3 was proposed.
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