Studies On Template And Modulation Actions Of Cholic Acid Aggregates On The Synthesis Of Inorganic Materials

Biomineralization is the study on the complex hierarchical structures of materials produced biologically, and the processes that lead to these biomaterials. In this field, the efforts of chemists can be roughly divided into three different areas:(1) the analysis of biological materials;(2) the design of new model systems to mimic physiological environment in vitro, such as hydrogel media; and (3) the development of new strategies of bioinspired material synthesis, like template methods.In this work, we have synthesized hollow silica microspheres by a biomimetic template method at first, and then have studied the highly oriented growth of inorganic KCl crystals in hydrogel media; at last, we have prepared conductive polymer composite materials based on a porous polymer substrate. It can be summarized as follows:(1) Hollow spherical silica has been successfully fabricated in mild conditions (room temperature, no organic solvent, one-step method) using cholic acid aggregates as templates in basic solutions. The structures of the synthesized silica materials were analyzed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The vesicle morphologies of the self-assembly aggregates of cholic acid in the presence of benzylamine were confirmed by Dynamic Light Scattering (DLS) and Phase Contrast Microscopy (PCM). The cholates were identified in FT-IR spectrum, confirmed the existence of organic templates. The mixture of hollow spherical and granular structure was obtained when n-butylamine or diethylamine was used as amine additives instead, while only granule in the case of diethylamine. The aggregates of 3-amino- propyltriethoxysiline (APES) with cholic acid, ammonium cholate and sodium cholate, have also been used as templates to prepare hollow silica spheres, where there were solid spheres existed in the products. The results were ascribed to the hydrogen bonding interactions between the organic templates and the inorganic precursors.(2) Low-molecular-weight (LMW) hydrogel is one of the quickly expanded research fields in recent years. Hydrogel system is an important kind of artificial media for biomineralization simulation. We have observed the oriented growth of potassium chloride (KC1) crystals and the dendritic patterns with high symmetry grown from the novel kind of LMW hydrogels derived from cholic acid. It was characterized by SEM equipped with Electron Energy Disperse Spectroscopy (EDS). The orientation of the patterns can hardly be changed by the concentration of either solutes or hydrogel matrix. The type of the hydrogel had great influence on KCl crystal morphologies, since the seaweed-like patters disordered in macroscopy have been obtained from another kind of LMW hydrogel derived from L-cystine. Crystal habit modifications of KCl crystals in aqueous solutions added with the hydrophilic groups of the hydrogelators through the special adsorptions with the specific crystal faces were studied. The hydrogel media have not only provided the sites for nucleation, selected the orientations of nucleating faces and crystal growth rates, but also allowed the translation of local symmetries to the whole dendritic patterns through periodic growth under the mass diffusion limited but stable microenvironment.(3) In the family of conductive polymer materials, which have attracted much attention because of their special features and potential applications in hi-tech aspects, polyaniline (PANI) is unique due to its electronic, thermoelectric and optical properties and good environmental stabilities. Preparation of PANI composites on porous polymer substrate could improve its mechanical stability and processibility. We have prepared conducting composite materials by the synthesis of PANI layers by a simple one-step chemical oxidative polymerization, based on the surface of a honeycomb ordered porous polycarbonate (PC) film prepared via water-assisted method from PC/CHCl3 solutions. Aniline monomers were pre-organized on the surfaces of the PC film through hydrogen bonding, and a PANI film was obtained by oxidation in situ. The surface and cross-section structures of the PANI/PC composite film were characterized by SEM, confirmed the role of the PC film as template. The results of thermogravimetric analysis (TGA) of the PANI/PC composite film showed higher thermal stability than PANI itself. The FT-IR spectrum confirmed the existence of hydrogen bonding interactions between PC and PANI. The electrical conductivity of the PANI/PC composite film was determined by the four-probe technique.In conclusion, the organic matrix with pre-organized ordered morphologies can serve as templates to modulate the growth of inorganic and organic materials. It could provide new strategies for material preparation and more information for deeply understanding biomineralization.