Functional Inorganics/polyelectrolyte Layer-by-Layer Assembled Films

Layer-by-layer (LbL) assembly, which was developed by Decher and co-workersin the early1990s, provides a simple and inexpensive way to fabricate various kindsof composite films with well-tailored chemical compositions and architectures on themicro-and nanoscales. Moreover, this method can be reduced to two processes:soaking multilayers in the solution of building blocks and then rising them to removethe physical adsorptive materials. Drying steps even can be omitted during the filmdeposition procedure. Thus LbL assembly is expected to be used for industrialproduction.Compared with polymer, inorganic matter has better mechanical, optical andelectrical properties. Thus, combining the advantages of the organic and inorganicmatter is an excellent idea to construct new materials. As we know, the layer-by-layerassembly method is a good way to fabricate hybrid films. In this dissertation，we usethis method to fabricate functional organic-inorganic films with sepiolite andgraphene oxide as nanofillers. Moreover, we proved layer-by-layer assembly is a goodway for the rapid and convenient fabrication of polymer nanocomposites, which has aprevalent meaning of guidance. The dissertation mainly includes the followingaspects:(1) Pyrene-based compounds have been widely used as fluorescent probes indetecting nitroaromatic explosives. Because the NACs like2,4,6-trinitrotoluene (TNT)and2,4-dinitrotoluene (DNT) can form non-fluorescence charge-transfer complexwith the pyrene excimer. Here, we prepared a film of poly(4-vinylpyridine)(P4VP)/1-pyrenebutyric acid-modified sepiolite (PBA-SEP) alternately assembled via hydrogen-bonded LbL assembly. Typically, the fluorescence quenching of the(P4VP/PBA-SEP)1(deposition cycles is1) film is70.4%in10s after exposure toDNT vapour at room temperature. This is one of the fastest fluorescence sensors forexplosives at present.(2) Graphene, a monolayer of tightly packed carbon atoms, is considered to be anexcellent two-dimensional nanofiller for polymer nanocomposites with its outstandingmechanical strength along with the potential for electrical and thermal properties.Owing to these remarkble properties, graphene can significantly improve the physicalproperties of the polymer matrix at very low loading. Here, we report the preparationof mechanically robust graphene oxide (GO) nanocomposite free-standing films byexponential layer-by-layer assembly (e-LbL). Compared with the pure polymer matrixmultilayers, the GO nanocomposite films achieve a nearly5times increase of theultimate tensile strength and Young’s modulus at GO content of6.4wt.%. The highmechanical property is mainly attributed to the homogeneous dispersion of the GOnanofillers.