The Layer-by-Layer Assembly Film Based On Halogen Bonding

Layer-by-layer assembly is a simple and practical nanostructures assembly technology. For the advantages of low cost, high quality film and widely used, it has become an important method to make super-thin nano-film, nano-composites, nano-devices and surface modification. PEI is a commonly used polymer. Compared with other polymers, PEI has a better solubility. Because the terminal of PEI chain has a large number of amino, we can modify PEI to gain the hyperbranched polymers that people need by grafting small molecules with certain function on the PEI. Halogen bonding is a weak non-covalent interaction which exists between electron-poor halogen atoms and electron-rich Lewis base. It has strong hydrophobicity. As a new driving force of layer-by-layer assembly, on the one hand, halogen bonding has enriched building elements of layer-by-layer assembly; on the other hand it has broadened the methods to control the structure and properties of multilayer. In this thesis, we used PEI as the core element. After modifying the amino of PEI, we used it to fabricate multilayer that based on halogen bonding. The experiments consist of two parts:(1) The synthesis of hyperbranched polymer which can be used as halogen bonding donor. First we synthesized iodine perfluorophenyl ether. Then iodine perfluopophenyl ether acid was synthesized and activated. Finally we used activated iodine perfluopophenyl ether acid to react with the amino of PEI to make iodine perfluorophenyl graft on the PEI;(2) Multilayer was fabricated by layer-by-layer assembly with PEI-IPhF4as halogen bonding donor and PVP as halogen bonding receptor. The layer-by-layer assembly process was monitored by UV-vis spectrometer. The surface morphology of multilayer was observed by atomic force microscopy (AFM). The interaction between building elements was characterized by X ray photoelectron spectroscopy (XPS). Because this multilayer used halogen bonding as driving force, it was different from traditional multilayer. There was only single charge-positive charge in the multilayer, so this multilayer can adsorb materials with negative charge, and the selective adsorption was achieved.