导电高分子精品课件

1、导电高分子第1页，共85页，2022年，5月20日，2点29分，星期三Introduction第2页，共85页，2022年，5月20日，2点29分，星期三Polymers were thought of as electrial insulators until the discovery that iodine-doped polyacetylene(聚乙炔) exhibited electrical conductivity many orders of magnitude higher than neutral polyacetylene. This discovery was publ

2、ished by Shirakawa, H., Louis, E., MacDiarmid, A., Heeger, A., (1977). As a result of this pioneering work, they received the 2000 Nobel Prize in Chemistry. Introduction第3页，共85页，2022年，5月20日，2点29分，星期三Nobel Prize in Chemistry 2000“For the discovery and development of conductive polymers”G. MacDiarmid

3、H.Shirakawa J.Heeger第4页，共85页，2022年，5月20日，2点29分，星期三黑格（Alan J. Heeger,1936 ）美国加利福尼亚大学的著名物理学家，2000年10月10日，因对导电聚合物的发现和发展而获得诺贝尔化学奖。Introduction第5页，共85页，2022年，5月20日，2点29分，星期三麦克迪尔米德（Alan G. MacDiarmid， 1937 ）美国宾夕法尼亚大学的著名化学家，2000年10月10日，因对导电聚合物的发现和发展而获得诺贝尔化学奖。Introduction第6页，共85页，2022年，5月20日，2点29分，星期三白川英树(H

4、ideki Shirakawa，1936 ) 日本筑波大学的著名化学家，2000年10月10日，因对导电聚合物的发现和发展而获得诺贝尔化学奖。Introduction第7页，共85页，2022年，5月20日，2点29分，星期三ConductivityIntroduction第8页，共85页，2022年，5月20日，2点29分，星期三The discovery of conductive polymers is unique in its accomplishment as a possible substitute(替代物) for metallic conductors and semico

5、nductors. Scientists from many disciplines are now combining expertise(专门技术) to study organic solids that exhibit remarkable conducting properties. A large number of organic compounds, which effectively transport charge are roughly divided into three groups i.e. charge transfer complexes/ion radical

6、(基) salts, organometallic species and conjugated organic polymers. Introduction第9页，共85页，2022年，5月20日，2点29分，星期三Electronically conducting polymers differ from all the familiar inorganic crystalline semiconductors in two importantfeatures that polymers are molecular in nature and lack long range order.

7、A key requirement for a polymer to become intrinsically(本征) electrically conducting is that there should be an overlap of molecular orbitals to allow the formation of delocalized(离域) molecular wave function. Besides this, molecular orbitals must be partially filled so that there is a free movement o

8、f electrons throughout the lattice.Introduction第10页，共85页，2022年，5月20日，2点29分，星期三Conducting polymers contain -electron backbone responsible for(是的原因) their unusual electronic properties such as electrical conductivity, low energy optical transitions, low ionization potential and high electron affinity.

9、 This extended(延长) -conjugated system of the conducting polymers have single and double bonds alternating along the polymer chain. The higher values of the electrical conductivity obtained in such organic polymers have led to the name synthetic metals. Introduction第11页，共85页，2022年，5月20日，2点29分，星期三Intr

10、oductionThe development of polymers with conductivities equal to semiconductors and metals have been presented in Table 1 and their corresponding structures are shown in Fig.1.第12页，共85页，2022年，5月20日，2点29分，星期三Introductionisothianaphthene:异硫茚；azulene:甘菊蓝；furan:呋喃第13页，共85页，2022年，5月20日，2点29分，星期三Introduct

11、ionPoly-acetylenePoly pyrrolePoly thiophenePoly anilinePoly-p-phenylenePoly-phenylene vinylenePoly-p-phenylene sulphidePoly-iso-thianaphthene第14页，共85页，2022年，5月20日，2点29分，星期三Historical background of electronically conducting polymers第15页，共85页，2022年，5月20日，2点29分，星期三Historical background of electronicall

12、y conducting polymersResearch on conducting polymers intensified(增强) soon after the discovery of poly(sulphur nitride) (SN)x in 1975 which becomes superconducting at low temperatures (Greene et al., 1975). Although, conducting polymer complexes in the form of tetracyano(四氰基) and tetraoxalato-platina

13、tes(四草酸铂酸盐), the Krogman salts charge transfer complexes had been known earlier, the significance lies in the rediscovery of PA in 1977 (initially discovered by Shirakawa et al., 1977 using a Ziegler Natta type polymerization catalyst) by MacDiarmid and Heeger, University of Pennsylvania(宾夕法尼亚). 重视第

14、16页，共85页，2022年，5月20日，2点29分，星期三They were able to enhance the electrical conductivity of PA (109 S cm1) by several orders i.e. 105 S cm1 by simple doping with oxidizing agents e.g. I2, AsF5, NOPF6 (p-doping) or reducing agents (n-doping) e.g. sodium napthalide(萘钠). This has generated renewed interest

15、of the scientific community towards the study and discovery of new conducting polymeric systems. Historical background of electronically conducting polymers第17页，共85页，2022年，5月20日，2点29分，星期三Poly-paraphenylene(对苯基) was synthesized by Ivory et al. (1979). It forms highly conducting charge transfer comple

16、xes with both n and p type dopants. Doping with AsF5 increases its conductivity to its values from 105 to 500 S cm1. Theoretical models and electron spin resonance measurements indicate that the charge transport in PPP is a polaron(极化子) /bipolaron. PPS(聚苯硫醚) was the first non-rigid, but not fully ca

17、rbon backbone linked conducting polymer. Its discovery was particularly exciting, since its property of solution processability opened the door for potentially obtaining commercially viable conducting plastics (Rabolt et al., 1980).Historical background of electronically conducting polymers第18页，共85页

18、，2022年，5月20日，2点29分，星期三Amongst polyheterocyclines(聚杂环), polypyrrole (PPY) has been investigated the most. The electrochemical oxidation of pyrrole in aqueous H2SO4 can be carried out on platinum electrode. The product is a conducting polymer known as Pyrrole Black Kanazawa et al. (1979) produced cohe

19、rent films of PPY with a conductivity of 100 S cm1 and exhibited excellent air stability. But the main hindrance(障碍) of its processability is in its insolubility in any organic solvents.Historical background of electronically conducting polymers第19页，共85页，2022年，5月20日，2点29分，星期三PTH(聚噻吩) shows remarkabl

20、e stability of both oxidized (p-doped) conducting form and its neutral (undoped) insulating form in both air and water. It shows high doping level upto 50% which may be attributed to its partially crystalline nature that has been confirmed by X-ray photoelectron spectroscopy studies. Many other cond

21、ucting polymers such as polyfuran(聚呋喃), polyindole(聚吲哚), polycarbazole(聚咔唑), polyaniline etc. have also been synthesized. Structures of some typical conducting polymers have been shown in Fig. 1.Historical background of electronically conducting polymers第20页，共85页，2022年，5月20日，2点29分，星期三Synthesis of co

22、nducting polymers第21页，共85页，2022年，5月20日，2点29分，星期三There is no singular method for synthesising polymers that can be transformed into conductive polymers, the incorporation of extended(延长) -electron conjugation(共轭) is of foremost importance. Conductive polymers except ionomeric(离子交联的) polymers may be s

23、ynthesised using standard methods of polymerisation including conventional as well as specific routes which include Witting(维狄希), Horner(霍纳) and Grignard(格林尼亚) reactions, polycondensation processes and metal catalysed polymerisation techniques. Oxidative coupling(偶合) with oxidising Lewis acid cataly

24、sts generally leads to polymers with aromatic or heterocyclic building blocks(构件).Synthesis of conducting polymers第22页，共85页，2022年，5月20日，2点29分，星期三Conductive polymers may be synthesised by any one of the following techniques:1. Chemical polymerisation2. Electrochemical polymerisation3. Photochemical p

25、olymerisation4. Metathesis(复分解) polymerisation5. Concentrated emulsion(浓乳液) polymerisation 6. Inclusion(夹杂) polymerisation7. Solid-state polymerisation8. Plasma(等离子体) polymerisation9. Pyrolysis(高温分解)10. Soluble precursor(前体) polymer preparationSynthesis of conducting polymers第23页，共85页，2022年，5月20日，2点

26、29分，星期三Among all the above categories, chemical polymerisation is the most useful method for preparing large amounts of conductive polymers, since it is performed without electrodes. Chemical polymerisation (oxidative coupling) is followed by the oxidation of monomers to a cation(阳离子) radical and th

27、eir coupling to form dications and the repetition(重复) of this process generates a polymer. All the classes of conjugated polymers may be synthesised by this technique.Synthesis of conducting polymers第24页，共85页，2022年，5月20日，2点29分，星期三Electrochemical polymerisation is normally carried out in a single- or

28、 dual-compartment(隔间) cell by adopting a standard three-electrode configuration in a supporting electrolyte, both dissolved in an appropriate(适当的) solvent. Electrochemical polymerisation can be carried out potentiometrically by using a suitable power supply (potentiogalvanostat).Synthesis of conduct

29、ing polymers第25页，共85页，2022年，5月20日，2点29分，星期三Generally, potentiostatic conditions are recommended to obtain thin films, while galvanostatic conditions are recommended to obtain thick films. The electrochemical technique has received wider attention both because of the simplicity and the added advantag

30、e of obtaining a conductive polymer being simultaneously doped. Besides this, a wider choice of cations and anions for use as “dopant ions” is available in the electrochemical polymerisation process. Free-standing(自由选定) as well as self-supporting conductive polymer films of desired thickness or geom

31、etry can be obtained. Synthesis of conducting polymers第26页，共85页，2022年，5月20日，2点29分，星期三Using this novel technique, a variety of conductive polymers like polypyrrole, polythiophene, polyaniline, polyphenylene oxide pyrrole and polyaniline/polymeric acid composite have been generated. Pyrrole in aqueous

32、 acetontrile solvent containing tetraethyl ammonium tetrafluoroborate was electropolymerised in a two-electrode electrochemical cell. Polypyrrole containing the BF4- ion (dopant) was obtained as a film deposited on the platinum electrode surface. Synthesis of conducting polymers第27页，共85页，2022年，5月20日

33、，2点29分，星期三This method has also been used to polymeric acetylene(乙炔). In an electrolytic cell, consisting of Pt as cathode and a Ni strip as anode, acetylene gas is passed over a solution comprising NiBr2 dissolved in CH3CN. On application of voltage varying from 5 to 40 V for about 50 min. polyacety

34、lene films can be easily grown on a Pt electrode. The degree of doping depends on the dopant concentration, voltage applied and the amount of charge passed.Synthesis of conducting polymers第28页，共85页，2022年，5月20日，2点29分，星期三Synthesis of conducting polymers第29页，共85页，2022年，5月20日，2点29分，星期三Photochemical poly

35、merisation takes place in the presence of sunlight. This technique utilises photons to initiate a polymerisation reaction in the presence of photosensitisers. Recently, pyrrole has been photopolymerised using a ruthenium(II) complex as photosensitiser. Under photoirradiation, Ru(II) is oxidised to R

36、u(III) and the polymerisation is initiated by a one-electron transfer oxidation process. Polypyrrole (PPy) films may be obtained by photosensitised polymerisation of benzo(C)thiophene(苯并噻吩) has been carried out in acetonitrile using CCl4 and tetrabutylammoniumbromide.Synthesis of conducting polymers

37、第30页，共85页，2022年，5月20日，2点29分，星期三Plasma(等离子体) polymerisation is a technique for preparing ultrathin uniform layers (500-100 ) that strongly adhere to an appropriate substrate. Electric glow discharge is used to create low-temperature “cold” plasma. The advantage of this technique is that it eliminates

38、 various steps needed for the conventional coating process.Synthesis of conducting polymers第31页，共85页，2022年，5月20日，2点29分，星期三Metathesis(复分解) polymerisation is unique, differing from all other polymerisations in that all the double bonds in the monomer remain in the polymer. It was a natural outgrowth (

39、发展) of Ziegler-Natta polymerisation in that the catalysts used are similar, and often identical(一样的), i.e. a transition metal compound plus usually an organometallic alkylating agent(烷基化剂). Metathesis polymerisation is further divided into three classes: ring-opening metathesis of cyclo-olefins(环状石蜡

40、) (ROMP); metathesis of alkynes(炔烃), acyclic(脂肪族的) or cyclic; and metathesis of diolefins(二烯). By far the greatest amount of work has been done on ROMP.Synthesis of conducting polymers第32页，共85页，2022年，5月20日，2点29分，星期三Pyrolysis(高温分解) is probably one of the oldest approach utilised to synthesise conduct

41、ive polymers by eliminating heteroatoms(杂原子) from the polymer by heating it to form extended aromatic structures. The product of polymer hydrolysis can be a film, powder or a fibre depending on the form and nature of the standing polymer(常规聚合物) including the pyrolysis condition.Synthesis of conducti

42、ng polymers第33页，共85页，2022年，5月20日，2点29分，星期三Nevertheless, conductive polymers have also been synthesised by other techniques such as chain polymerisation, step-growth polymerisation, chemical vapour deposition, solid-state polymerisation, soluble precursor polymer preparation, concentrated emulsion po

43、lymerisation etc. However, most of these techniques are time-consuming and involve the use of costly chemicals.Synthesis of conducting polymers第34页，共85页，2022年，5月20日，2点29分，星期三Conduction mechanism第35页，共85页，2022年，5月20日，2点29分，星期三Conduction mechanismThe mechanism of conduction in such polymers is very co

44、mplex since such a material exhibits conductivity across a range of about fifteen orders of magnitude and many involve different mechanisms within different regimes(情景). Conducting polymers show enhanced electrical conductivity by several orders of magnitude of doping. The concept of solitons(光孤子),

45、polarons and bipolarons has been used to explain the electronic phenomena in these systems (Heeger, 1986). 第36页，共85页，2022年，5月20日，2点29分，星期三什么是Soliton光孤子是传播时几乎没有能量损失并能保持其形状(即使与其他波相碰撞)的波，这种现象首先是在水中被观察到的。孤子以光脉冲的形式被用于光纤传输系统以提高距离和性能。光孤子信号按照数字编码方法编码后进入光缆。基于光孤子的设备发射通过光缆传播而又不会出现色散的激光短脉冲。光弧子是一种特殊的ps 数量级上的超短光脉

46、冲，由于它在光纤的反常色散区，群速度色散和非线性效应相互平衡，因而经过光纤长距离传输后，波形和速度都保持不变。光弧子通信就是利用光弧子作为载体实现长距离无畸变的通信，在零误码的情况下信息传递可达万里之遥。 第37页，共85页，2022年，5月20日，2点29分，星期三polaron来作用于电子，改变电子的状态与能量，并伴随电子通 过点阵运动。电子及其周围的极化场所构成的总体，称 为极化子。极化子是离子晶体中基本的载流子。极化子 的尺寸由电子周围畸变场区域的大小确定。当这个区域 比晶格常数大很多时，称为大极化子，这时晶体可作为 连续介质处理;当畸变区等于或小于晶格常数时，称为 小极化子，此时必须

47、考虑晶体结构的原子性，用晶格模 型处理。第38页，共85页，2022年，5月20日，2点29分，星期三Conductivity in conducting polymers is influenced by a variety of factors including polaron length, the conjugation length, the overall chain length and by the charge transfer to adjacent molecules (Kroschwitz, 1988). These are explained by large nu

48、mber of models based on intersoliton(中间光极子) hopping, hopping between localized states assisted by lattice vibrations, intra-chain hopping of bipolarons, variable range hopping in 3-dimensions and charging energy limited tunneling between conducting domains.Conduction mechanism第39页，共85页，2022年，5月20日，2

49、点29分，星期三Conductivity improvement techniques第40页，共85页，2022年，5月20日，2点29分，星期三The conductivity of a polymer can be increased several-fold by doping it with an oxidative/reductive substituents(取代基) or by donor/acceptor(给体/受体) radicals. Shirakawa and Ikeda discovered that doping of polyacetylene (PA) with

50、 metallic regimes(态) increases its conductivity by 9-13 orders of magnitude. Doping is accomplished by chemical methods of direct exposure of the conjugated polymer to a charge transfer agent (dopant) in the gas or solution phase, or by electrochemical oxidation or reduction.Conductivity improvement

51、 techniques-doping第41页，共85页，2022年，5月20日，2点29分，星期三The doping is usually quantitative and the carrier concentration is directly proportional to the dopant concentration. Doping of conductive polymers involves random dispersion or aggregation of dopants in molar concentrations in the disordered structu

52、re of entangled chain and fibrils(原纤). Polymer doping leads to the formation of conjugational defects, viz. solitons, polarons or bipolarons in the polymer chain. An x-ray diffraction study on iodine-doped polyacetylene chain increases with donor doping but decreases on acceptor doping.Conductivity

53、improvement techniques-doping第42页，共85页，2022年，5月20日，2点29分，星期三The presence of localised electronic states of energies less than the band-gap arising from changes in local bond order, including the formation of solitons, polarons and bipolarons have led to the possibility of new types of charge conduct

54、ion present in these polymer systems. Chart 1 gives the charge and spin characteristics of these defects.Conductivity improvement techniques-doping第43页，共85页，2022年，5月20日，2点29分，星期三Conductivity improvement techniques-doping第44页，共85页，2022年，5月20日，2点29分，星期三Polymers may be doped by the following techniques

55、:1. gaseous doping2. solution doping3. electrochemical doping4. self doping5. radiation-induced doping and6. ion-exchange doping.Conductivity improvement techniques-doping第45页，共85页，2022年，5月20日，2点29分，星期三Conductivity improvement techniques-dopingOf these, the first three techniques are widely used bec

56、ause of convenience and low cost. In the gaseous doping process, polymers are exposed to the vapours of the use of a solvent in which all the products of doping are soluble.第46页，共85页，2022年，5月20日，2点29分，星期三1,4-Poly(butadiene(丁二烯) polymers having a non-conjugated (共轭) backbone have been doped with halo

57、gen(卤素) to form semiconductors. Effective doping of polymer anions during chemical polymerisation of pyrrole using Fe3+ based oxidants and electrolytes increases the conductivity several-fold. Vadera and Kumar have demonstrated that certain dopants could give rise to magnetic ordering in these polym

58、ers along with the electron acceptor (e.g. iodine, FeCl3, AsF5, etc.) or electron donor (e.g. Na, Li, etc.) to the polymer which is considered to generate positive carriers (holes) or negative carriers (electrons) in the -conjugated system.Conductivity improvement techniques-doping第47页，共85页，2022年，5月

59、20日，2点29分，星期三Doping agents or dopants are either strong reducing agents or strong oxidising agents. They may be neutral molecules and compounds or inorganic salts which can easily form ions, organic dopants and polymeric dopants. The nature of dopants play an important role in the stability of condu

60、ctive polymers. For example, perchloric acid doped polyacetylene is not sensitive to water and oxygen. Conductivity improvement techniques-doping第48页，共85页，2022年，5月20日，2点29分，星期三Similarly, electrochemical doping of polyacetylene with sodium fluoride makes it more resistant to oxygen. When poly(3-methy