Polypyrrole is a commonConductive polymer。The pure pyrrole monomer presents a colorless oily liquid at room temperature. It is a five membered heterocyclic molecule of C, N, with a boiling point of 129.8 ℃ and a density of 0.97g/cmthree, slightly soluble in water.
The pure pyrrole monomer presents a colorless oily liquid at room temperature. It is a five membered heterocyclic molecule of C, N, with a boiling point of 129.8 ℃, a density of 0.97g/cm, and is slightly soluble in water.
Property: a heterocyclic conjugate type that is studied and used frequentlyConductive polymer, usuallyamorphous Black solid, with pyrrole as monomer, afterelectrochemical oxidation PolymerizedConductivityFilm, oxidant is usually threeFerric chloride、Ammonium persulfateEtc.Or use chemistryAggregation methodsynthesis,electrochemistryanodic oxidation Pyrrole is also an effective means to prepare polypyrrole.It has good air stability and is easy to form film by electrochemical polymerizationConductive polymer, insoluble and fusible.It is used in acidic aqueous solution and various organic compoundselectrolyteZhongdu Energychemical oxidation Polymerization film-forming, whichconductivityAnd mechanical strengthanion, solvent, pH value, temperature and other polymerization conditions are closely related.Conductive polypyrrole has conjugated chain oxidation and corresponding anion doping structure, and its conductivity can reach 102~103S/cm,tensile strength Up to 50~100MPa and good electrochemical oxidation reductionreversibility。Conductivity mechanism: PPy structure has carbonSingle bondandCarbon carbon double bondThe double bond is a conjugated structure alternately arranged by σ electrons andπ electronThe σ electron is fixed and cannot move freelycarbon atomInterphase formationcovalent bond。Conjugated double bondThe two π electrons in are not fixed on a certain carbon atom. They can be transferred from one carbon atom to another, that is, they tend to extend on the whole molecular chain.That is, π in the moleculeElectronic cloudThe overlap ofenergy band, π electrons are similar to those in metal conductorsfree electron。When there is an electric fieldpi bondThe electrons of can move along the molecular chain.Therefore, PPy can conduct electricity.In polymers, pyrroleStructural unitThey are mainly connected with each other in α position, when there isSubstituentHourpolymerizationCannot proceed.Electrochemical oxidationAggregation methodIt can be directly generated on the electrode surfaceConductivityThe conductivity of the film can reach 102S/cm, and its stability is better thanPolyacetylene。The oxidation potential of polypyrrole is about 1V lower than that of its monomer.Polypyrrole can also be used chemicallyDoping methodAfter dopingCounterionThe introduction ofIonic conductionAbility.PolypyrroleConductive materialFor example, it can be used as a special electrode, and also used as an electrical display materialConjugated polymerPolypyrrole also has certain photoconductive properties.The polypyrrole doped with small anions will age slowly in the air, leading to the reduction of its conductivity.Polypyrrole doped with large hydrophobic anions can be stored in air for several years without significant change.
（1）ion exchange resinCompared with traditional ion exchange resin, this material combines electrochemistry and ion exchange together, which can facilitate regeneration, reduce energy consumption and pollution.
(3) Proton exchange membrane: the proton exchange membrane serves as the proton exchange membranefuel cellThe core components of fuel cell directly determine the performance of fuel cell.Introduce PPy into it to prepare compositeProton exchange membraneHelps improvecomposite membraneOfthermal stability, alcohol resistance, swelling, etc.
(4) Electrocatalysis: PPy film has unique doping and dedoping properties, which can be targeted into manyreactantyesCatalysisAnd provide electrocatalytic efficiency and practical application value.
（5）Secondary batteryElectrode material: PPy has high conductivityEnvironmental stabilityGood, reversible electrochemistryRedoxIt is an ideal electrode material for polymer secondary battery due to its characteristics and strong charge storage capacity
Polypyrrole can be passed by pyrrole monomerChemical oxidation methodperhapselectrochemical method Made.Chemical polymerization is to oxidize monomer in a certain reaction medium orOrganometalliccouplingTo get conjugateLong chainThe molecules complete a doping process at the same time.The synthetic process of this method is simple, the cost is low, and it is suitable for mass production.useChemical methodWhen preparing polypyrrole, the product is generally solid polypyrrole powder, which is difficult to dissolve in generalOrganic solvent，Mechanical propertiesIt is also poor and difficult to process.The mechanism for the synthesis of polypyrrole products: first, when there is oxidant in the systemElectroneutralityA polypyrrole monomer molecule ofcationFree radical。Then two cation free radicals collide and combine in the system to form a double cation dipyrrole containing two cation free radicals. At this time, the double cation in the system undergoes disproportionation to form a neutral dipyrrole.The electrically neutral dipyrrole will combine with the cationic free radicals in the system to formTripolypyrroleCationic free radical of, generated by disproportionationTrimerThe polypyrrole with long molecular chain is finally generated from the polypyrrole with long molecular chain.Electrochemical polymerization is to adoptelectrode potential As the energy required for polymerization, after a period of reaction, a layer of polymer will be deposited on the electrode surface to obtainConjugated polymerMembrane.By controlling the polymerization conditions, such as the type of electrolyte, the concentration of pyrrole monomer, solvent, polymerization voltage, current size and temperature, varioushigh polymerMembrane.When conducting electrochemical polymerization, platinum, goldstainless steel, nickel and other inert metals orConductive glass、graphiteAnd glassCarbon electrodeIt is used as electrode.The polymerization mechanism when using electrochemical method to prepare polypyrrole is similar to that when using chemical oxidation method. It can also be explained by free radical mechanism: first, under the action of electric field, the pyrrole monomer molecule will lose electrons on the surface of the electrode and become a cationic free radical, and then the free radical will combine with another monomer to become pyrroleDimer。After chain growth, polypyrrole is finally obtainedMacromolecular chain。Generally speaking, when the chemical oxidation polymerization or electrochemical polymerization is used to prepare polypyrrole, the products obtained are black solids. When the chemical oxidation polymerization is used to prepare polypyrrole, the products are generally black powder, and a layer of PPy film will be obtained on the electrode surface through the electrochemical polymerization.
