Study On Mineralization By Using Solution And Thermal Gel Of Hydroxypropylmethyl Cellulose As Templates

Nowadays, it arouses great interest to prepare novel materials with special morphology and property by using organic template. Structure and character of the template have great effect on structure and morphology of the materials. Hydroxypropylmethylcellulose (HPMC) which possesses weak polarity groups, like polyhydroxy groups and ether groups, will transform to hydrogel when temperature increases. Thus it is a promising and novel template. This work plans to investigate the effect of HPMC, especially the hydrogel of HPMC, on the mineralization process.Rheological method was used to study the gel transformation procedure of HPMC. It is further proved that the gelation is due to the hydrophobic association of the macromolecules of HPMC. Gel temperature increased, while gel strength decreased as the concentration of HPMC solution increased. Additives possessing electrolyte property reduce the gel temperature, while those possessing surfactant property elevate the gel temperature. Hydroxyl containing additives may influence the gelation of HPMC according to the result of competition of their electrolyte property and surfactant property.Solution and thermal hydrogel of HPMC was used as organic template to synthesize calcium carbonate and calcium phosphate, respectively. The effect of template on the crystal polymorph and morphology of products were explored by X-ray diffract meter (XRD) and scanning electron microscope (SEM). Also thermogravimetry(TG) and Fourier transform infrared spectroscopy(FTIR) was used to investigate the essential of influence of the template.As for the system to synthesize CaCO3, results showed that the presence of HPMC induced the formation of aragonite. And its content became higher when the concentration of solution increased or when rotating the system with presence of HPMC. Moreover, it can be seen from SEM that bundle-like CaCO3 appeared and became more with the increase of concentration. The structure and shape of the crystal had close relationship with the condition of mineralization. On the other hand, for the first time, CaCO3 was synthesized in HPMC gel, SEM results indicated that a special structure, long bar with some slight slots at intervals on the surface, of the crystals was found. TG and FTIR results showed that HPMC performed as a template through ether and polyhydroxy groups along its chains. Moreover, HPMC gel template also modulated the growth of crystals through the regular micro-region ofhydrophobic association caused by the self-assembly of the macromolecules and network structure of hydrogel.In the case of the calcium phosphate, the results of XRD and SEM showed that hydroxyapatite (HA) with different crystalline degree and morphological character was synthesized in the solution and gel of HPMC, and the crystallization of the gel system was the best. Besides the increase of the temperature, the content of HPMC in the gel system resulted in the rise of the crystalline degree. From the results of the FTIR and the data of conductivity, it can be seen that the presence of the organic template affected the crystallization of the calcium phosphate. On the basis of all the experiments and conclusions, a probable mechanism of the synthetic process was proposed.