The Study Of Different Surface Active Groups Of Pamam Calcium Phosphate Crystallization Behavior

Two new polyamidoamine (PAMAM) dendrimers with peripheral maltose and palmitoyl groups were synthesized and characterized by 1H NMR and FT-IR. The properties of the PAMAM dendrimer and the mixture of the PAMAM dendrimer and Ca²⁺ in solution were observed by UV and AFM. The UV data demonstrated that the Ca²⁺ ions were coordinated to N or O atoms of the PAMAM when the Ca²⁺ ions were added into the solution of the PAMAM. The AFM result proved the self-assembly behavior was found when the dendrimer themselves and the mixture of the PAMAM dendrimer and Ca²⁺ in solution, which is the first stage of forming calcium phosphate.The calcium phosphate nanoparticles were achieved by hydrothermal crystallization in the presence of different templates, which were the PAMAM dendrimers with peripheral maltose and palmitoyl groups, in different concentrations, reaction time and pH value, and characterized by FTIR, XRD, TEM and TG-DTA respectively. These result indicated that there were three steps for the calcium phosphate depositional process, which was from DCPD to DCPA and finally to HAP phase. The TEM test result demonstrated that calcium phosphate nanoparticles presented dissimilarity shape and size, which resulted from the different mode of action between the dendrimer themselves under different condition.According to the test data, we thought the formation of calcium phosphate was part to the mechanism of mesoscale self-assembly organic-inorganic hybrid aggregate.In the presence of template, the Ca²⁺ ions firstly entered the cavity of PAMAM and were coordinated to N or O atoms of the dendrimer. Then the HPO42? group also entered the cavity owing to the electric charge equilibrium function. The DCPD phase was deposited when the density of Ca²⁺ and HPO42? attained certain degree, and the varied topography was formed for the self-assembly behavior of the dendrimer molecule when calcium phosphate crystals were growth. Under the hydrothermal condition, the DCPD transformed to DCPA and HAP, at the last gained calcium phosphate nanoparticles with dissimilarity shape and size.