| Layer-by-Layer(LbL) assembly has been widely used as a versatile method for fabricating multilayer thin films with tailored structure and composition. In this field, scientists have obtained precious experiment data, showing that multilayer structure can be tuned by several parameters. However, stucture controlling of LbL film assembled in organic solvents has been rarely reported. In this thesis, we mainly worked on the effect of organic solvents on LbL assembly via hydrogen bonding or halogen bonding.We first designed and synthesized poly(8-(4-carboxy-phenoxy)-octyl acrylate)(PCPOA), poly(2-(4-carboxy-phenoxy)-ethyl acrylate)(PCPEA) and poly(3-(4-pyridyl)-propyl acrylate)(PPyPA), polymers bearing either carboxyl group or pyridine group in their side chains. Radius of polymers in THF/ethanol mixed solvents with different compositions was obtained using the Dissipative Particle Dynamic (DPD) simulation. Combined with the polymer radius in solvents, LbL assembly behavior of PCPOA/PPyPA was anticipated.Using LbL technique, PCPOA/PPyPA LbL films were prepared from THF/ethanol solvent mixture. Comparing the IR spectra of cast film of polymer and that of LbL film, the formation of the new broad peak, and shift of carboxyl group stretching vibration and pyridine group in-plain breathing vibration inferred that films were mainly driven by hydrogen bonding. UV-vis spectra of polymer LbL assembly in different mixed solvents showed that thinner films were formed when polymers take an extended conformation in the solution. PCPEA, which has two methylene groups in the side chain, was also assembled into multilayer films with PPyPA in different solvent mixtures. We found that the deviation from linear increase of film growth curved became larger when PCPEA were used instead of PCPOA in the LbL assembly.LbL assembly via halogen bonding was first reported by our team. In chapter 3, we introduced hydrogen bonding unit into halogen bonding donor polymers and investigated the effect of solvents on LbL assembly of polymers driven by both halogen bonding or hydrogen bonding.We synthesized poly (4-iodo-2, 3, 5, 6-tetrafluoro-phenoxy) ethyl methacrylate(PIPEMA), poly(carboxy ethyl acrylate)(PCEA) and copolymers including the above units. Controlling the composition of IPEMA unit, polymers containing 30%, 55% and 80% IPEMA unit were obtained, noted as PCI30, PCI55, PCI80. Poly(3-(3-pyridyl)-propyl methacrylate)(PPyPMA) was also synthesized and characterized.We prepared PCEA/PPyPMA, PCI30/PPyPMA, PCI55/PPyPMA, PCI80/PPyPMA, PIPEMA/PPyPMA LbL films from chloroform, THF, butanone and THF/butanone mixed solvents, respectively. We found that LbL assembly via halogen bonding was sensitive to organic solvents. Films can not be obtained in many kinds of solvents. While LbL films via hydrogen bonding were successfully formed in various solvents in a stable linear increase model. Additionally, amount of polymers adsorbed in the film increased as hydrogen bonding sites in polymers increased. The LbL behavior of copolymers/PPyPMA pair was similar to purely driven LbL assembly when the content of one component was dominant in the copolymer.Finally, we investigated the stability of multilayer films in different organic solvents. We found that solvents such as chloroform, THF, DMF and pyridine would destroy the halogen-bonding films assembled from butanone. DMF even destroyed all kinds of films in our investigated system. However, the stability of halogen-bonding films was elevated after its post-treatment under 180 oC in vacuum oven. The preliminary study showed that polymers in the film might react with each other in the post-treatment. Thus, the film stability increased. |
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