CALCIUM PHOSPHATE SOL-GEL COMBUSTION SYNTHESIS AND ITS APPLICATION IN BIO-INSPIRED COMPOSITE PRODUCTION

251 pagesCrystalline calcium phosphate, CaP, in the form of carbonated hydroxyapatite, is the majority inorganic constituent of bone and teeth. Aqueous syntheses and amorphous/poorly crystalline precursors are established routes to producing CaP. Determining new pathways to crystallize CaP from non-aqueous media allows for more possibilities in hierarchically structured self assembled inorganic-organic bio-inspired composites. Specifically, in this thesis, I focus on understanding the mechanism of the sol-gel combustion synthesis of calcium phosphates by tracking the solution reactions of P(OEt)3, Ca(NO3)2 and a selection of organic fuels, as well as following the evolution of solid-state products as a function of temperature. Varying the amount of fuel (e.g., 2(2-methoxyethoxy) acetic acid, 22MEAA) and oxidizer (Ca(NO3)2) in the initial reaction mixture gives insight into the reaction pathway. The fuel study revealed that the amphiphilic 22MEAA with both ether and carboxylic acid functional groups, reduces the crystallization temperature at which hydroxyapatite, Ca10(PO4)6OH2, forms from >500°C in the absence of fuel to 150ºC. Furthermore, the combined use of diethylene glycol dimethyl ether, DIGLYME, and acetic acid at four times the molar amount of 22MEAA is able to lower the crystallization temperature to as low as 125ºC. The sol-gel combustion reaction yields powders with high porosities, which are retained upon further heating of the solids. With the same fuels and the same P:fuel ratio, varying the Ca:P ratio, as well as introducing other calcium sources (e.g., CaCl2) yields the production of other calcium phosphate phases. In addition to identifying and characterizing a new fuel and fuel mixture for sol-gel combustion synthesis, this study defines a parameter space that can produce various forms of calcium phosphates at relatively low temperatures and in non-aqueous solutions. Finally, after defining the parameter space, work was done to integrate the combustion sol-gel reaction with polymers to establish a pathway for the production of structurally stable, highly porous, inorganic-organic composites