Preparation And Properties Of Conducting Polymers And Their Composites With Two-dimensional Nanomaterials

Since the conducting polymers were first synthesized in the last century, they have beenstudied extensively in the fields of chemistry, materials science, electronics, physics andbiomedicine due to their excellent conductivity and unique redox state. With the rapiddevelopment of nanotechnology, a large number of conductive polymer micro-andnanostructures with different morphologies have been synthesized and studied in the past twodecades, which showed better properties in many aspects than conventional bulk material. As aresult, fabrication of conducting polymers with micro-and nanostructures has become a hotspot in material preparation. The interfacial behavior of conducting polymer micro-andnanostructures has attracted much attention in recent years. Conducting polymer nanostructuresexhibit high interfacial activity due to their small size, high surface energy and controllablemorphology, doping and oxidation state of the conducting polymer may also cause variation ofthe surface condition. Hitherto, the most common method to control the interfacial behavior ofthe conducting polymer is adding modified groups and kinds of surfactants. The commonmethod to control the interfacial behavior of the conducting polymer is constructing coarsesurface or combining materials with low surface energy. Very few research reports aboutcontrolling the surface wetting property by constructing micro-and nanostructures ofconducting polymer. Therefore, how to control the surface wetting property of conductingpolymers merely through preparing different micro-and nanostructures by changing experimental method has become one of the research topics.The development of novel materials continuously demands to have the versatility to meetthe different needs of practical application, the individual components of the conductingpolymer is difficult to fulfill the actual needs. Hence, combining functional inorganic materialswith the conducting polymer to fabricate binary or multi conducting polymer nanocompositeshas become one of the research focus in recent years. These nanocomposites which combinethe performance and advantages of different materials, increase the range of materialapplications and improve the properties of nanocomposites through the synergy effect betweeneach component. There are many methods to prepare conducting polymer nanocomposites.Different combinations and forces among each component prepared by distinct methods causesthe diverse properties of nanocomposites. Simplification is the trend and the target ofpreparation methods, which is to obtain conducting polymer nanocomposites with variousmorphologies, controllable size and excellent properties.This paper stands from the view of preparing conducting polymer nanostructures and theirnanocomposites with inorganic two-dimensional nanosheets, by using different syntheticmethods, such as chemical vapor phase polymerization, electrospinning method, hydrothermalmethod and self-assembly method. Firstly, through the design of micro-and nanostructures oftwo different polypyrrole (PPy) film, we have fabricated two types of PPy films which showedhydrophilic and hydrophobic properties, respectively. Furthermore, we have studied the water-oil separation and oil absorbing properties of the PPy-based nanofibers film. Secondly, we havesynthesized algae-like MoS2/PPy nanocomposites and MoS2/PEDOT/Pd nanocompositesthrough a hydrothermal and redox polymerization method, and evaluated their peroxidase-likecatalytic activity for H2O2and glucose detection. Thirdly, since polyaniline nanofiber exhibitedpoor cycling stability as electrochemical capacitors, we have fabricated core-shell structuredpolyaniline (PANi) nanofibers with MoS2nanosheets or reduced graphene oxide as the shelllayers, and further studied their electrochemical capacitor performance and the mechanism ofimproving electrochemical cycle stability. The detail research is shown as follows:1. By using chemical gas phase polymerization, pyrrole vapor polymerized at gas-water interface between air and FeCl3solution, and porous free-standing polypyrrole films wereobtained. The as-prepared PPy free-standing film has good mechanical strength, and has auniform distribution of micron diameter pore structures. It was found that the film thicknessand pore diameter are proportional to the FeCl3concentration and polymerization time. Thefilm we obtained by controlling the condition of1M FeCl3and1h owned super-hydrophilicproperties, that contact angle with water reach0owithin0.5s.In order to achieve hydrophobic PPy film by only adjusting the micro-nanostructures, wehave prepared polyacrylonitrile (PAN) nanofibers firstly through an electrospinning technique.Then PPy was grown on the surface of PAN nanofibers to form core-shell nanostructuredPAN@PPy composite through chemical gas phase polymerization between pyrrole monomerand HNO3vapor as an oxidant. By controlling the reaction conditions, we got the film with thebest properties with polymerization time of8h. The as-synthesized PAN@PPy nanofiber filmexhibited hydrophobic properties with a contact angle with water of about135o.The film alsoshowed excellent oil-absorbing properties towards various kinds of oils, wherein the content ofthe motor oil adsorption reached106.5g/g, and had a good reusability. PAN@PPy nanofiberfilm can also be used as an oil-water separation membrane, which can completely separate10mL of CCl4/water mixture within8s.2. An unique algae-like MoS2/PPy nanocomposite was prepared in a one-pot synthesis forthe first time via hydrothermal reaction by using the redox reaction between ammoniumtetrathiomolybdate and pyrrole monomer. This unique algae-like structure is accumulatedbetween the MoS2layers coated by PPy. The as-prepared MoS2/PPy nanocomposite was fullycharacterized and then used as a catalyst with peroxidase-like activity, exhibiting enhancedcatalytic activity to produce a blue color reaction, which might arise from the unique algaestructure compacted with sheets as well as the synergistic effects between MoS2surface and thearound PPy. The catalytic activity of the MoS2/PPy composite is much higher than that of pureMoS2nanoflowers, pure PPy and their physical mixture, which can detect H2O2in the linearrange from50μM to2mM in acetate buffer solution (pH=4.0).Comparing with PPy, PEDOT is easier to generate on the surface of MoS2nanosheets, and exhibits the ability to react with sodium tetrachloropalladate to produce metallic Pdnanoparticles. Therefore, we have synthesized MoS2/PEDOT nanocomposites through thesimilar hydrothermal reaction, and further prepared MoS2/PEDOT/Pd ternary nanocompositesvia an in situ self-reduction process. The as-prepared nanocomposites have a flower-likestructure accumulated by nanosheets stacking, which possess a large specific surface area. ThePd nanoparticles disperse well on the surface of every sheet and have a uniform particle size.The composite exhibit an excellent peroxidase-like catalytic performance toward H2O2andglucose detecting.3. A hierarchical algae-like core-shell structured PANi@MoS2nanocomposites wereprepared through a one-pot hydrothermal reaction by using the redox property of ammoniumtetrathiomolybdate and polyaniline nanofibers. The as-prepared hierarchical PANi@MoS2electrode have a specific capacity of450F·g-1under0.5M H2SO4, higher than that of338F·g-1of PANi nanofibers electrode. Besides, as the core-shell structure enhanced the structuralstability, the electrochemical cycle stability of PANi@MoS2electrode increased significantlycomparing with PANi nanofibers electrode, which retain80%in specific capacity after2000charge-discharge process, higher than47%of that with PANi nanofibers electrode.To further increasing the electrochemical cycling stability of polyaniline nanofibers, wechose rGO as a larger area and more excellent mechanical materials to synthesize algae-likePANi@rGO nanocomposite with a hierarchical core-shell structure via a hydrothermal reactionby using the redox property of graphene oxide and polyaniline nanofibers. The as-preparedhierarchical PANi@rGO electrode have a high specific capacity of490F·g-1under0.5M H2SO4.The composites we prepared exhibited a robust structure to maintain the core-shell morphologyduring the charge-discharge process, which caused PANi@rGO with excellent electrochemicalstability. Comparing to the fist cycle, the specific capacity of PANi@rGO electrode after1500charge-discharge processes still remained95.9%.