Directional Assembly Of Hierarchical Structures: Aniline Oligomers As The Model Precursors

Compared to their bulk counterpart, nanomaterials and their assemblies usuallyexhibit unique physical and chemical properties, which often attract scientists toexplore their preparation, characterization and application. Therefore, design,synthesis and characterization of polyaniline nanostructures and their assemblies hasaroused widespread interest in science and technology. It is believed that anilineoligomers is closely related to the formation of polyaniline hierarchical architectures.This dissertation contains:(1) synthesis and characterization of aniline oligomer;(2)synthesis and characterization of linear aniline oligomer, and its self-assembly intoultralong nanofibres;(3) proposal mechanism of aniline oligomer self-assembly intovarious hierarchical architectures;(4) application of the aniline oligomers hierarchicalarchitecture in preparing superhydrophobic surface and other fields.A series of preparation conditions, such as polymerization time, temperature,solvent composition, pH and oxidant concentration, etc. were investigated, duringwhich a large number of aniline oligomer hierarchical architectures were obtained.The aniline oligomers molecular structure of a typical flower-like microsphere, as anexample, was analyzed. A series of techniques, such as scanning electron microscopy(SEM), matrix assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF MS), gas chromatography-mass spectrometry (GC/MS), elementalanalysis, X-ray diffraction analysis (XRD), ultraviolet-visible spectroscopy (UV-VisSpectra), and Fourier Transform infrared spectroscopy (FTIR) were used tocharacterization of the aniline oligomers and their hierarchical architectures. Based onthe experimental results, the molecular structure of the aniline oligomers, which mightprovide information to identify the intermolecular interaction force that drive anilineoligomers assemble into well-ordered hierarchical structures, was proposed.Aniline tetramer ultralong nanofibre was firstly produced in an aqueoussolution containing n-propanol via chemical oxidation of aniline by usingammonium persulfate as the oxidant. The product was characterized by a series oftechniques, including scanning electron microscopy (SEM), matrix assisted laserdesorption ionization time of flight mass spectrometry (MALDI-TOF MS), gas chromatography-mass spectrometry (GC/MS), elemental analysis, X-ray diffractionanalysis (XRD), UV-visible spectroscopy (UV-Vis Spectra), Fourier transforminfrared (FTIR) and nuclear magnetic resonance (NMR). According to theexperimental results, it is concluded that the linear aniline tetramer was in reductionstate. The assembly of aniline tetramer into the ultarlong nanofibers was alsoinvestigated by molecular simulation (Material Studio), which is a promise methodto study the self-assembly mechanism of small molecules.Aniline trimer which contains quinone imine structural unit was used as anexample to study the self-assembly of the aniline oligomer into the hierarchicalarchitectures, and the directional assembly mechanism was proposed. It was assumedthat the aniline oligomer has an asymmetrical structure, a variety of intermolecularinteraction forces (hydrogen bonding, π-π stacking interactions, etc.) were available todrive the aniline oligomer molecules to self-assemble into highly ordered hierarchicalarchitectures in different ways. Influenced by the intermolecular interaction force(static electricity, hydrophobic interaction, etc.) between aniline oligomers andmolecules constituting the environment, aniline oligomer nanostructure can furtherself-assemble into three-dimensional hierarchical architectures, such as flower-like,sea urchin-like microspheres. The diversity and complexity of aniline oligomerinteraction forces between molecules (such as hydrogen bonding, π-π stackinginteractions, hydrophobic interaction, etc.) were interpreted the hierarchicalarchitectures formation process.The wettability of solid surface modified with aniline oligomer hierarchicalarchitecture, sea urchin-like microspheres, was investigated. Water contact angle wasas high as153.7°. The glass slide modified with urchin-like microspheres which wasprepared in situ polymerization medium has the contact angle of137.8°, whichdemonstrate that aniline oligomers can be used to control the wettability of the solidsurface.In conclusion, the materials with different hierarchical structures can bedirectional assembled by controlling the preparation conditions and their propertiescan be adjusted.