Controllable Synthesis And Properties Of Polyaniline Nanostructures

Conducting polymers,such as polyaniline,polypyrrole,polythiophene,and poly acetylene,have been widely used in electronic,electrochemical and optical fields due to their conjugated ?-electron system.Among the family of conducting polymers,polyaniline has unique electrical,electrochemical and optical properties since its doping level can be readily controlled by a simple acid doping/base dedoping process.In recent years,polyaniline nanostructures possess dual advantages of both low-dimensional system and organic conductors,which have potential applications in a variety of fields,such as biosensors,chemical sensors,molecular conducting wires,gas separation membranes and actuation.In the thesis,polyaniline nanostructures have been synthesized by chemical oxidative polymerization of aniline and its derivatives.The molecular structures,sizes,and morphologies of polyaniline nanostructures can be controlled by adjusting the reaction parameters.The possible formation mechanisms of polyaniline nanostructures have been proposed.The electrochemical and biosensing performances of polyaniline nanostructure have been researched.The main results are concluded as follows:(1)Necklace-like polyaniline nanochains assembled by elliptical nanoparticles have been synthesized in chitosan aqueous solution by a facile dispersion polymerization method.The dimensions of polyaniline nanochains are in the range of 20-100 nm.The reaction conditions such as reaction times,and the concentrations of chitosan,aniline and dopant acid have profound influences on the morphologies and sizes of polyaniline nanostructures.FTIR and UV-vis spectra reveal that polyaniline nanochains are typical doped polyaniline in its emeraldine salt form.Open circuit potential measurements show that the polymerization rate of aniline has a substantial decrease due to the steric effects of chitosan.A self-assembly process of elliptical nanoparticles has been proposed for the formation of necklace-like polyaniline nanochains with fluctuant diameters.Polypyrrole-Chitosan Composite(PCC)nanospheres with uniform diameters have also been synthesized by chemical oxidation polymerization of pyrrole in chitosan aqueous solution.It is found that the diameters of PCC nanospheres can be adjusted in the range of 20-100 nm by tuning the concentrations of chitosan and pyrrole.The resulting PCC nanospheres possess both the biocompatibility and bioactivity of chitosan and electroactivity of polypyrrole.(2)Hollow self-doped poly(aniline-co-3-aminobenzeneboronic acid)micro/nanostructures such as hollow microspheres,aligned pearls,and nanotubes,have been synthesized by chemical oxidative copolymerization of aniline and 3-aminobenzeneboronic acid.The molar ratio of aniline and 3-aminobenzeneboronic acid plays an important role in the formation of polyaniline hollow structures.As the molar concentration of 3-aminobenzeneboronic acid is increased,hollow microspheres,hollow aligned pearls,and nanotubes are formed,respectively.The formation of hollow polyaniline micro/nanostructures is possibly related to the self-assembly of polyaniline oligomers at the early stage of copolymerization reaction.FTIR spectra reveal that BO3-groups are bonded to the aromatic rings in polyaniline chains.The cyclic voltammograms of poly(aniline-co-3-aminobenzeneboronic acid)demonstrate that the ratios of boronic acid moieties can improve the electrochemical activity and the conductivity of copolymers.(3)Poly(anilineboronic acid)(PABA)nanofibers with U-shaped morphologies have been synthesized successfully by chemical polymerization of 3-aminophenylboronic acid in the presence of cetyltrimethylammonium bromide(CTAB)and NaF.As the concentration of the surfactant increasing,the diameters of self-doped polyaniline nanofibers are increased,and the surface of the nanofibers is becoming rougher.FTIR and UV-vis spectra reveal that BO3-groups are bonded to the aromatic rings in self-doped polyaniline chains.The PABA nanofibers exhibit excellent electrochemical redox activity and high sensitive detection of D-glucose in the phosphate-buffered saline stock solution.(4)Polyaniline nanostructures including nanofibers,nanorings,and polyaniline nanocapsules,have been synthesized successfully by chemical polymerization of aniline monomer in V2O5-H2O2-H3PO4 mixture.It is found that the substantial oxidant is VOPO4·2H2O nanoplates,and the H3PO4 concentrations are critical for the controlled synthesis of polyaniline nanostructures.As the H3PO4 concentrations are 0.2 mol/L,0.7 mol/L,and 3.6 mol/L,polyaniline nanofiber with diameters of 20 nm,polyaniline nanorings with sizes of 0.2-1.1 ?m,and polyaniline nanocapsules are obtained,respectively.A possible in-situ oxidative templating process has been proposed for the formation of poly aniline nanostructures.FTIR and UV-vis spectra reveal that poly aniline nanostructures are emeraldine salt.Cyclic voltammograms curve shows polyaniline nanostructure exhibit good electrochemical redox activity,which is similar to that of conventional polyaniline.