Pedot Nanotube/Wire Composite:Preparation,Properties and Applications

Author:Wang Fang

Supervisor:ma yu hong


Degree Year:2018





Poly(3,4-ethylenedioxythiophene)(PEDOT),as one of electroactive polymers,has been widely used in a variety of applications,including light-emitting diodes,gas sensors,anti-static,passive components,display devices and electromagnetic shielding due to its advantages in high conductivity,environmental benign,excellent thermal stability and high transparency.PEDOT nanotubes/wires have large aspect ratio,leading to high charge/discharge capacities and short diffusion distances for ion transport,which leads to fast charge/discharge rates.Recently,nanotubes and nanowires of PEDOT have been prepared by electropolymerization with AAO or inorganic oxide nanotubes as templates.However,a scalable chemical synthetic route to prepare bulk quantities of PEDOT nanowires has still been remained elusive so far.The PEDOT system is particularly difficult to form fibrillar or tubular morphology.Techniques,such as nanofiber seeding,activated seeding and interfacial polymerizations,have been widely used in synthesizing nanofibers of polyaniline and polypyrrole.However,only granular powders were obtained when these techniques were applied to the chemical oxidation polymerization of EDOT.It is of great importance to develop a scable route for the fabrication of PEDOT nanotube wire with high aspect ratios.Furthermore,the obtained PEDOT nanotube wire composite has important significance for the development of high-performance polymer-based electrodes and energy storage materials.It is also very helpful to understand the relationship between structure and properties of PEDOT nanocomposite.Following are main text and research:1.A composite of a core-shell structured nanowires with ZnO as a core and conductive PEDOT as a shell was prepared.At first,the hexagonal ZnO nanowires,with diameter of about 80-100 nm and length 4-5 μm,were fabricated by hydrothermal synthesis process.Then a thick layer of poly(trifluoroethyl methacrylate)-block-poly(sodium styrene sulfonate)(PTFEMA-b-PSSNa)was grafted from the surface of ZnO nanowires via atom transfer free radical polymerization(ATRP).At last,with the ZnO@PTFEMA-b-PSSNa as a template and the PSSNa chain as the counterion dopant,PEDOT was precipitated onto the surface of the template to form the composite of ZnO@PEDOT.With the evaluation of the EDOT polymerization,the thickness of the PEDOT layer increased steadily.However,when the concentration of EDOT increasesd to a certain extent,the ZnO nanowires templates were dissolved at last and then PEDOT particles were produced due to increasing of the acidity during the oxidation polymerization of the EDOT.In this case,the product was the mixture of the nanotubes and particles of PEDOT:PPSNa.The electrochemical capacitances of the composites with different structures were investigated with cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques with three-electrode cell configuration.The maximum specific capacitance of composites increased 35%compared to pure PEDOT2.The three-layer coaxial cable composite HNTs@PEDOT@MnO2 were successfully synthesized.The hybrid composite of PEDOT and halloysite nanotubes(HNTs)was prepared by a two-step process.First,PSSNa was grafted onto HNTs via ATRP.Then with the HNTs-g-PSS as a template and the grafted PSS chains as the counterion dopant,PEDOT was precipitated onto the template via in situ oxidization polymerization of EDOT to form HNTs@PEDOT hybrid composites.The conductivity of HNTs@PEDOT could reach up to 9.35 S/cm with the content of 40%HNTs-g-PSS,which increased almost 78 times than that of pure PEDOT(about 0.12 S/cm)obtained at the similar condition.When the content of HNTs-g-PSS is 20%,the specific capacitance of HNTs@PEDOT composites is 55%higher than pure PEDOT.In order to further increase the specific capacitance of HNTs@PEDOT,a layer of MnO2 was deposited onto the surface of HNTs@PEDOT by simply mixing HNTs@PEDOT and KMnO4 solution.The specific capacitance of HNTs@PEDOT@MnO2 can reach up to 159 F/g at a constant current density of 1.0 A/g in 1 M Na2SO4 solution.The specific capacitance can still maintain 82.4%after 1000 cycles,showing good cycling stability.3.A novel composite with HNTs-PEDOT hybrid as conductive filler and poly(vinylidene fluoride)(PVDF)as flexible polymer matrix was investigated.First,HNTs-PEDOT hybrid,with PEDOT coated onto both the inner and out surfaces of the HNTs tubes as negative chargers on the surface of HNTs,are synthesized via chemical oxidative polymerization of EDOT with HNTs as templates.The conductivity of HNTs-PEDOT hybrid with 50 wt%HNTs is up to 12.89 S/cm,which is greater 100 times of pure PEDOT(about 0.12 S/cm)prepared at the similar condition.Then the as-prepared HNTs-PEDOT are exploited as conductive filler to prepare PVDF based flexible composites HNTs-PEDOT/PVDF with high dielectric constant.With introducing of HNTs-PEDOT into PVDF matrix,it makes a phase convert of PVDF from a phase to β phase which have been demonstrated by both the XRD and DSC.The β phase provides higher electroactive properties than the other crystalline structures(α,γ,and δ)of the PVDF.The dielectric properties of the HNTs-PEDOT/PVDF with different weight fraction of HNTs-PEDOT have been measured at room temperature in the frequency range from 1000 Hz to 30 MHz.The results show that the dielectric constant and dielectric loss of the composite increase with the amount of HNTs-PEDOT loaded.At the percolation threshold value(fHNTs-PFEDOT=0.11),the dielectric constant can reach up to 641.45 at 1000 Hz,which is attractive to prepared flexible materials.