The Study On Interfacial Composite Films Of Polymer-lanthanide Complex

The thesis is mainly studied the preparation of the polymer-Lanthanide complex thin film,which is divided by three parts including the preparation of the polymer-Lanthanide complex,fabrication of the composite films and dynamic on the film fabrication process. Using water soluble poly(diallyl dimethylammonium) chloride and poly(acrylic acid)(PDDA and PAA) as research system, we tried to introduce the Lanthanide ions(Ln3+) into the self-assembly film.Firstly, we prepared the polymer-Lanthanide complex by PAA and Ln3+ ions and studied various factors which influenced on the properties of the complex, such as pH value, molar ratio and different preparation methods. The higher pH value is favorable for the ionization of PAA and coordination with Ln3+ ions. However when pH was above 7.5, Ln(OH)3 precipitation was formed by Ln3+ ions and hydroxyl ions(OH-), which reduced the concentration of Ln3+ ions. So the p H was fixed at 6.0 where the ionization of PAA was about 50%. Increasing the molar ratio of PAA and Cerium chloride(CeCl3)([AA]:[Ce]) would introduce more carboxylate groups(COO-).It was found that when molar ratio was over 6 at pH 6, the complex nanoparticles were dispersed evenly in the solutions due to the excessive negative charges; when molar ratio reached to 10, the system remained the stability for long time. Preparation of the homogeneous polymer-Lanthanide complex was a kinetically-controlled process. When PAA solution was drop-wise added into Ce3+ion solution, the nuclei would be easily formed. As more PAA chains were added into the system,the PAA-Ce complex particles would grow up and have the largest particle size with the good kinetical stability.Then the stable and homogeneous complex particles were layer-by-layer(LbL) assembled with PDDA to fabricate the thin film. Only when the pH value of PDDA was larger than 2 where PAA began to ionize could the film be prepared. If the film was fabricated by the larger particle size, the thickness and roughness of the films would also increase. The coordination would decrease the separation value between asymmetric and the symmetric vibration of carboxylate groups while the electrostatic interaction would not influence the value. Different Ln3+ ions endowed the thin film with fluorescence property. Introducing Europium ions(Eu3+) and Terbiumions(Tb3+) made the film show red and green light under the UV irradiation.In [PDDA/(PAA@Ce)]20 film, PDDA and PAA have electrostatic interaction while PAA and Ce3+ ion have coordination. There is a dynamic equilibrium. Increasing the PDDA concentration would enhance the electrostatic interaction between PAA and PDDA and make the equilibrium shift, which caused the film to become thin and smooth. The growth trend of the film monitored by QCM was different when two kinds of PAA-Ce complexes were applied to fabricate the film.Protocol 2 particles were small and had low zeta-potential. So the particles were easy to aggregate and Lb L assembly of PDDA and Protocol 2 particles showed exponential thickness growth.Protocol 3 particles were big and had high zeta-potential. PDDA chains would squeeze Protocol 3particles during the assembly process. So it showed linear growth.When the films were incubated in different environment, the force in the film changed and the equilibrium shifted. Incubation in PDDA solution, electrostatic association was strengthened and coordination became weak while incubation in CeCl3 solution, coordination was enhanced and electrostatic interaction became weak. Incubation in salt whose concentration was above 0.5mol/L for 24 h, the film would be dissolved.