Surfactant-encapsulated Polyoxometalate Complex: From Self-assembly To Hybrid Polymer Materials

Polyoxometalates (POMs) are the molecular clusters of the early transition metal oxides, especially for the elements of vanadium, molybdenum and tungsten. POMs have the variety in composition and structure, which makes them have great potential in catalyst, medicine, magnetism, luminescence, nonlinear optics, proton conductivity etc. However, the development of materials and devices based on POMs was greatly restricted because of their poor processibility, and great efforts have tried to improve the functionality performance of POMs with the assistance of other matrices. Organic molecules and polymers are considered as the suitable candidates for POMs matrices due to their organizable properties and good processibility. In this thesis, by taking the strategy from electrostatic interaction, we encapsulated POMs with the cationic surfactants and prepared the organic/inorganic supramolecular complexes. In such complexes, we can use the surfactants to induce the assembly of POMs and adjust their properties, and even incorporate POMs into the polymer matrices.Firstly, we study the self-assembly behavior of the complexes. We found that the complexes were amphiphilic arising form the coexistence of hydrophobic alkyl chains of surfactants and the hydrophilic POMs core. Such an amphiphilic character caused the complex readily to aggregate in solution. By controlling the polarity of the solvent, we successfully obtained the spherical and stable assemblies of the complex. Furthermore, the POMs'properties are influenced by the microenvironment of the spherical assemblies. For example, the porous Mo132 clusters, which can uptake and release Li⁺, were incorporated into the assemblies. The rate of Li⁺ releasing from Mo132 can be lowered by the spatial effect of surfactants. By adjusting the number of surfactants, we successfully manipulate the releasing rate of Li⁺. Besides, the microenvironment of the spherical assemblies could act as soft template during the metal-reduction process of POMs. We found the reaction of reduced H₃PMo₁₂O₄₀ clusters and HAuCl4 is very interesting when this process was carried out in the spherical assemblies. The formation of Au are limited and induced by the surfactant templates and finally a unique flower-like Au nanostructure was formed.Except for the using of above spherical assemblies to favorable the functionality performance of POMs, we also used the polymerizable surfactants to encapsulate the POMs and thus obtained the polymerizable complexes. The complexes could be copolymerized with the organic monomers, such as styrene and methyl methacrylate, leading to hybrid polymer materials. The hybrid bulk materials and latexes were easily prepared by using the bulk polymerization methods and miniemulsion polymerization methods, respectively. The optical properties of POMs such as luminescence and colors are both well retained in the hybrid materials.In summary, we have fabricated different polyoxometalate-hybrid assemblies and polymer materials, by using the surfactants to drive and link them into the organic and polymer matrices. Either the assemblies or the hybrid polymer materials exhibit the synergy effect between the POMs and the matrices.