The Preparation Of Rare Earth Polymer Complex And Layer-by-Layer Assembly Films

In this paper, the complexation behavior of PAA and lanthanide (Ln) ions was schematically investigated. On the basis of the complexation behavior of binary complex, we prepared PVPON-Ce-PAA ternary complex successfully under different pH values. Finally, we prepared PVPON-PAA containing Ce3+ions layer-by-layer assembly films.The complexation behavior of PAA and lanthanide is a complicated process. The factors, such as pH value, molar ratio and concentration, greatly affect the formation of the PAA-Ln complex. COO" has stronger interaction with lanthanides than COOH. Complexation of PAA and lanthanide ions happens at pH values higher than2.0where PAA exhibits ionization. When the pH value of the solution is higher than7.5, lanthanide ions will form the precipitation of Ln(OH)3, hydroxide will interrupt the complexation of PAA and Ln ions. When PAA and lanthanide formed the complex, it would precipitate out from the solution. When the concentration of lanthanide ions is less than1.0×10-3mol/L or the molar ratio exceeds the certain number, the PAA-Ln complex can homogeneously distribute in the solution. If we utilize PAA to remove lanthanide ions from the solution, we should calculate how much PAA to be used and consider the ionization degree of PAA at certain pH value.Hydrogen bond and coordination bond can both exist in the PAA-Ce-PVPON ternary complex in the pH region2.5-4.0. With pH value increasing, hydrogen bonding interaction gradually decreases, and the coordination interaction increases. The Ce content in the complex is increasing with pH value increasing, this is due to the increasing ionization of PAA. As the ionization of PAA increasing, the ratio of COO-is increasing. COO" has stronger interaction with lanthanides than COOH. So the Ce content increases with pH value increasing.When pH value is less than3.5, we can prepare (PVPON-Ce-PAA)n layer-by-layer assembly films successfully. As pH value increases to3.5, Ce ions can coordinate with COO-, which can hinder the formation of hydrogen bond, so it can not form films when pH value is higher than3.5. In the region pH<3.5, the thickness of the film is decreasing with the concentration of Ce ions increasing.As for (PVPON-PAA-Ce)n layer-by-layer assembly films, hydrogen bond and coordination bond can both exist in the (PVPON-PAA-Ce)n films in the region2.5<pH<3.5. At the Ce ions concentration0.01mol/L, we can add the Ce ions into the (PVPON-PAA)n films without breaking the film.