Alkali-Guided Synthesis Of Polyaniline Micro/Nanostructures And Their Application

Polyaniline (PANI) is an important member in the family of "synthetic metals"that has been widely studied for a variety of applications ranging from lightweightbatteries, electromagnetic shielding devices, anticorrosion coatings, optical orelectronic devices, gas-separation membranes, and chemical or biological sensors etc.for its low cost, easy synthesis, good processibility, excellent environmental stabilityand reversible acid/base doping/dedoping chemistry. Recently, micro/nanostructuredpolyaniline has attracted special attention in both chemical and material fieldsbecause of the rapid emergence and development of nanoscience and nanotechnology.The researchers are re-examining various aspects of chemistry and physics ofpolyaniline under the "nano" scopes, thus make it becoming an importantlow-dimensional material.Up to now, there have been many reports on polyaniline micro/nanostructures,which were produced with various strategies such as templates, surfactants, interfaceand self-assembly method and so on. All those micro/nanostructures were wellprepared and each method had its strongpoint. Nevertheless, one great challenge is tofabricate functional, controlable structures with micro/nanoscale features in a facileway, at a low cost, and with a high throughput. As one of conducting polymers,polyaniline can change from an initial insulating state to an electrically conductingstate after protonic doping treatment. Therefore, polyaniline was usually synthesizedat lower pH condition. However, it has been proved in our research works that thetype of polyaniline micro/nanostructures related to pH sensitively on the syntheticmethod employed, which has not got enough attention previously. As we know,low-dimensional structures play an important role in determining material propertiesand promising potential application. Therefore, we should not only think of theimprovement of the electrically conducting properties, but also pay attention to theproperties of structural materal. Recently, some reports have noted this phenomenon,and tabled a proposal to synthesize polyaniline micro/nanostructures with wider rangeof pH.In this thesis, we succeeded in synthesizing multi morphologies of polyanilinemicro/nanostructures by oxidative polymerization of aniline (An) in aqueous alkalinesolution without any external physical or chemical templates, dopants and additives.We discussed the changing of morphologies, molecular structures and thepolymerization mechanism in this alkaline condition. By using this "Alkali-guided"method, we not only realized the semiconducting intrinstic properties of the produces,but also present a new approach to obtain many kinds of low-dimensional structuralmaterals, and gave an opportunity to apply this method in the fields of functionalbiomaterials and structural materials. The main results are summarized as follows:(1) "Alkali-guided" method is an effective and easy way to synthesize polyanilinemicro/nanostructures without external physical or chemical templates, dopants andadditives. Only by changing the pH or the concentration of aniline, the controllablepolyaniline structures from 1D nanotubes to 3D hollow microspheres could beobtained by the "Alkali-guided" method. As a whole, spheres became dominatingwhen the molar ratio of aniline monomer to sodium hydroxide (shortening asAn/NaOH) was less than 1: 1, well, seamless hollow microspheres were got in higherpH value combined with lower [An];when the molar ratio of An/NaOH was morethan 1: 1, nanotubes were dominating, but, ringent hollow microspheres were formedtype of polyaniline micro/nanostructures related to pH sensitively on the syntheticmethod employed, which has not got enough attention previously. As we know,low-dimensional structures play an important role in determining material propertiesand promising potential application. Therefore, we should not only think of theimprovement of the electrically conducting properties, but also pay attention to theproperties of structural materal. Recently, some reports have noted this phenomenon,and tabled a proposal to synthesize polyaniline micro/nanostructures with wider rangeof pH.In this thesis, we succeeded in synthesizing multi morphologies of polyanilinemicro/nanostructures by oxidative polymerization of aniline (An) in aqueous alkalinesolution without any external physical or chemical templates, dopants and additives.We discussed the changing of morphologies, molecular structures and thepolymerization mechanism in this alkaline condition. By using this "Alkali-guided"method, we not only realized the semiconducting intrinstic properties of the produces,but also present a new approach to obtain many kinds of low-dimensional structuralmaterals, and gave an opportunity to apply this method in the fields of functionalbiomaterials and structural materials. The main results are summarized as follows:(1) "Alkali-guided" method is an effective and easy way to synthesize polyanilinemicro/nanostructures without external physical or chemical templates, dopants andadditives. Only by changing the pH or the concentration of aniline, the controllablepolyaniline structures from 1D nanotubes to 3D hollow microspheres could beobtained by the "Alkali-guided" method. As a whole, spheres became dominatingwhen the molar ratio of aniline monomer to sodium hydroxide (shortening asAn/NaOH) was less than 1: 1, well, seamless hollow microspheres were got in higherpH value combined with lower [An];when the molar ratio of An/NaOH was morethan 1: 1, nanotubes were dominating, but, ringent hollow microspheres were formedThese works not only realized the composition of sugar and polyaniline, this isimpossible in acidic system, but also provided a novel functional biomaterial. Sincethe microspheres might act as a sort of chiral stationary phase, they showed apotential application in liquid chromatography.(5) The crystal structure of rigid, hollow, racemic binaphthyl poly(ether ketone)macrocycles has been elucidated by the single crystal X-ray analysis. Multitudinalinteractions were identified within the chiral space group P212121. The structuralanalysis revealed that this macrocyclic compound contains an elliptic chiral cavitywith a size of 9.80 × 5.18 ?, which is similar to that of cyclodextrins. The knowledgeabout the interaction sites and the structure of the binaphthyl macrocycle provides aunique opportunity to understand its molecular or chiral recognition properties.(6) The composite nanotubes of PANI with above sulfonic chiral binaphthyl-basedmacrocycle as dopants were prepared by a self-assembly method. XRD wasperformed to prove the composite structures. It was found that the sulfonic monomerswere tetrabasic acids, which was estimated by the results of elementary analysis. Inaddition, we redoped the sulfonic monomers on the glucose-containing polyanilinemicrospheres. EDX was performed to prove the composite microstructures. Thediscussion of the stability of the microspheres confirmed our belief that this kind ofmicrostructures could be used as chiral stationary phases. They are under continuinginvestigation.