Tunneling Effect in Polythiophene

Polythiophene has been chemically synthesized using 2,5– dibromothiophene by debromination with magnesium, catalyzed by nickel chloride. The synthesized polymer was undoped using liquid ammonia and then doped again using 5% (wt/volume) aqueous FeCl₃ for 2.5, 5 and 10 hour duration. Characterization of undoped as well as doped samples using elemental analysis and FTIR has been carried out. Elemental analysis shows that concentration of Fe⁺ atoms increases as the duration of doping increases. The FTIR spectrum reveals the complex formation between FeCl₃ and polythiophene. All samples were pressed into pellets of about 1cm in diameter. The pellets were coated with gold (Au) on one side and with aluminum (Al) on other side using vacuum deposition technique. I–V measurements of undoped and FeCl₃ doped samples, after coating have been carried out using two probe method. I–V measurements, at room temperature, were carried out by applying d. c. voltage with +ve potential to the side of the pellet coated with Au and –ve potential to Al from 0 V to 1 V in step of 0.01 V and then from 1V to 15 V in step of 0.5 V. The measurements were again carried out after interchanging the polarity of the applied voltage. These characteristics are just similar to the characteristics of conventional tunnel diode in forward bias condition and like Schottky diode in reverse bias condition. Various parameters of tunnel diode such as figure of merit, voltage spread, noise figure etc are calculated using the measurements carried out. Noise figure value of undoped polythiophene is very close to ideal value. The performance of all FeCl₃ doped sample reduces, however value of the current ratio I_p/I_v (figure of merit) value for 5 hr. FeCl₃ doped polythiophene sample matches with that of silicon (Si) tunnel diode.     

聚噻吩/多壁碳纳米管复合材料结构与导电机理的研究

从结构和相互作用方面对聚噻吩(PTh)/多壁碳纳米管(MWNTs)复合材料进行了研究, 结果表明: 一方面聚噻吩本身的结构对其导电性能有一定的影响, 另一方面MWNTs作为一种掺杂剂, 和聚噻吩之间存在强的相互作用, 电子从MWNTs转移到聚噻吩. MWNTs和它周围被掺杂的聚噻吩通过π-π共轭作用形成相对独立的导电单元, 在复合材料的导电体系中起到主要作用, 随着这种导电单元数量的增加直至相互接触, 形成大的导电体系, 复合材料的电导率达到最大值.     

Novel Cross‐Linked Conducting Polythiophene with Yellow‐Green‐Light‐Emitting Properties and Good Thermal Stability

A novel conjugated polythiophene derivative with polymethacrylate attaching to the polymer backbone via an alkyl spacer was successfully synthesized. A methacrylate‐substituted thiophene monomer, 3‐(hexyl methacrylate)thiophene was prepared and polymerized by free radical polymerization, followed by an electrochemical polymerization. The resulting polymer as a yellow‐green‐light emitter, has potential applications in photoelectronics area.     

聚噻吩/多壁碳纳米管复合材料的导电性能

通过共混多壁碳纳米管(MWNTs)和聚噻吩(PTh), 制备了PTh/MWNTs复合材料, 复合材料表现出良好的导电性能(电导率达16.1 S/m). 通过Raman, TG, XPS, UV-Vis等对复合材料进行了分析, 结果表明, MWNTs和 PTh之间存在强的相互作用, MWNTs上的离域电子与噻吩共轭主链上的π电子之间形成π-π共轭, 电子从MWNTs转移到聚噻吩, 增加了噻吩主链的有效共轭长度, 提高了复合材料的导电性能. FESEM分析表明, MWNTs和它周围被掺杂的聚噻吩通过π-π共轭作用结合在一起, 形成相对独立的导电单元, 在复合材料的导电体系中起到主要作用.     

Facile Optimal Synthesis of Inherently Electroconductive Polythiophene Nanoparticles

The straight dope : Polythiophene (PTh) nanoparticles with a narrow size distribution were successfully synthesized by a chemical oxidative polymerization (see image). The highest conductivity of virgin PTh is 3.1×10^?4 S cm^?1 and can be dramatically enhanced to 50 S cm^?1 by doping in iodine vapor.

     

Synthesis and Photovoltaic Properties of Polythiophene Incorporating with 3,4-Difluorothiophene Units

Two polythiophene derivatives using fluorine atoms and hexyl or hexyloxy group as electron-withdrawing and donating substituents have been synthesized. The introduction of fluorine atoms to the polythiophene backbones simultaneously lowers the HOMO and narrows the bandgap, and the stronger electron-donating ability of hexyloxy side chain further reduces the bandgap. As a result, poly[3-hexylthiophene-2,5-diyl-alt-3,4-difluorothiophene] （PHTDFT） shows HOMO and bandgap of -5.31/1.83 eV and poly[3,4-dihexyloxythiophene-2,5-diyl-alt-3,4-di- fluorothiophene] （PDHOTDFT） shows HOMO and bandgap of -5.14/1.68 eV, both are lower than --4.76/2.02 eV of P3HT. Benefiting from the lower HOMO, PHTDFT：PC61BM （1 ＂ 1） polymer solar cells obtain a power conversion efficiency of 1.11% and an impressed open-circuit voltage of 0.79 V under solar illumination AM1.5 （100 mW/cm2）.     

固相法制备聚噻吩/聚吡咯/二氧化钛膜及电化学腐蚀性能

在水蒸气气氛下,制备出表面富含羟基的纳米Ti O_2颗粒,然后在室温和氧化剂三氯化铁存在下,通过化学固相氧化法,在不锈钢表面制备出聚噻吩/聚吡咯/Ti O2(PTH/PPy/TiO_2)薄膜。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、热重分析(TG)、电化学阻抗(EIS)等技术手段对产物的微观形貌、热稳定性和耐腐蚀性能进行了研究,并讨论了不同纳米TiO_2含量对复合材料的结构和性能的影响。结果表明,在其使用温度(20~300℃)下,PTH/PPy/6%Ti O_2(质量分数)膜热分解温度为450℃,能够满足其使用要求。用PTH/PPy/TiO_2膜保护的不锈钢比裸露的不锈钢的自腐蚀电位高出0.8 V以上,而腐蚀电流密度降低了2个数量级。TiO_2的添加明显的提高了PTH/PPy材料的抑制腐蚀的能力,并且由于TiO_2的加入能够使聚合物与无机纳米粒子之间能够紧密地结合在一起,减少膜的缺陷,增大复合材料与金属基体的力学性能,使得膜结构更加的致密,从而减缓不锈钢的腐蚀。     

Influence of Side‐Chain Composition on Polythiophene Properties and Supramolecular Assembly of Anionic Polythiophene Derivatives

A series of 10 polythiophene derivatives is reported, in which each polymer has a different percentage of carboxylic acid‐bearing repeat units. The properties of these polymers are explored under acidic conditions, where the carboxylic acid moieties remain neutral, and under basic conditions, where the carboxylic acid units become anionic carboxylates. The properties that are examined for both solutions and films include UV–vis absorption spectroscopy, photoluminescence spectroscopy, and red‐edge optical band gaps. All the properties studied are strongly dependent both on protonation state and percentage of carboxylic acid/carboxylate side chains along the polymer backbone. The anionic form of each polythiophene derivative was also used in layer‐by‐layer film deposition with a cationic phosphonium polyelectrolyte. The film growth process was studied by spectroscopic techniques to assess the influence of side‐chain composition on the film growth and optical properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

聚噻吩制备条件对其结构和导电性能的影响

通过改变聚噻吩合成条件(温度、浓度、反应时间)得到各种不同样品, 用FESEM, FTIR光谱, Raman光谱, XRD, UV-Vis光谱和TG等手段对样品进行研究. 结果表明, 不同的制备条件会影响噻吩环的连接方式, 直接影响聚噻吩结构的分布. 导电性能研究表明, 聚噻吩的结构差异和其导电性能直接相关, 实验证明以α-α相连接的聚噻吩有更高的电导率.     

一维取代聚噻吩的电子性能

报道了3种取代聚噻吩,3-己基聚噻吩(P3HT)、3,4-二戊基聚噻吩(P34PT)、3-辛氧基聚噻吩(P3OOT)的合成方法1、H-NMR测试结果及UV-Vis吸收光谱和荧光光谱分析结果。用密度泛函方法计算了无取代噻吩、3-乙基噻吩、3,4-二乙基噻吩、3-乙氧基噻吩二聚体的电子性能。随聚合度的提高,聚合物能隙变窄。无取代噻吩二聚体的能隙为4.216 eV,重复单元长度为0.392 7 nm;乙基取代噻吩二聚体的能隙为4.733 eV,重复单元长度为0.393 9 nm;乙氧基取代噻吩二聚体的能隙为3.890 eV,重复单元长度为0.390 8 nm;双乙基取代噻吩二聚体的能隙为5.168 eV,重复单元长度为0.392 5 nm。理论变化规律与实验结果基本一致。     

低聚噻吩衍生物单体的合成及其聚合物薄膜的电致变色性能

合成了两种低聚噻吩衍生物单体:2,3':4',2'-三噻吩(I3T)和5,5'-二醛基-2,3':4',2'-三噻吩(OHC-I3T-CHO).通过电化学方法对单体I3T和OHC-I3T-CHO进行了聚合,制备了相应的聚噻吩衍生物.研究了聚噻吩衍生物薄膜的电致变色性能.当外加一定电压时,基于单体I3T的聚噻吩衍生物薄膜可以在淡黄色和淡蓝色之间发生可逆的颜色变化,基于单体OHC-I3T-CHO的聚噻吩衍生物薄膜能在红色和墨绿色间发生可逆的颜色变化.     

炭黑表面含氧量对HDPE—CB复合物导电性能的影响

通过硝酸氧化处理炭黑（CB）,使其表面含氧量（氧元素与碳元素的摩尔百分比）由1．0％（CB1）提高到7．0％（CB2）。分别以CB1和CB2为填料,以高密度聚乙烯（HDPE）为基体,制备了两种导电复合材料。与碳粒子填充极性聚合物相反,表面含氧量高的CB2填充HDPE复合物的渗流阈值低。采用SEM、动态电渗流效应和Payne效应分析了两种炭黑在HDPE中的分散和凝聚特征。结果表明：CB2在HDPE中分散更不均匀,更容易凝聚形成网络。炭黑在非极性HDPE中凝聚形成导电网络的能力随炭黑表面含氧量的增加而提高。     

Synthesis,Characterization and Electrorheological Properties of Polyindene/Kaolinite Composites

In this study, synthesis, characterization and electrorheological (ER) properties of polyindene (PIN) and polyindene/kaolinite composites were carried out by cationic radical polymerization using FeCl₃ as the oxidizing agent. The homopolymer and composites, containing different amounts of PIN were characterized by FTIR spectroscopy, thermo‐gravimetric (TGA) analyses, scanning electron microscopy (SEM) and dynamic light scattering (DLS) methods. The conductivity and dielectric properties of PIN and PIN/kaolinite composites were determined. Suspensions of PIN and PIN/kaolinite composites were prepared in silicone oil (SO), at a series of concentrations (c=5–25 m/m %). The effects of concentration, shear rate, electric field strength, frequency, temperature and promoter on ER activities of suspensions were investigated.     

Electrical Properties Investigation in PA12/PANI Composites

Summary: Volume conducting PA-12 based composites powders were chemically prepared by in situ polymerization and aniline doping at room temperature. These kinds of polyamide / PANI composites were investigated regarding their electrical properties. Their ac and dc electrical properties measured in the frequency range of 10⁻²–10⁷ Hz are reported and the frequency dependence of electrical conductivity was investigated as a function of PANI concentration leading to the determination of the conductivity. The experimental conductivity was found to increase continuously with PANI content and explained by percolation theory with a relatively low percolation threshold of about 0.4 wt.%. The dielectric behavior of various PANI polymer composites has been characterized by the critical frequency ω_c (denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour). Modelling the conductivity behavior versus volume fraction using Slupkowski approach has revealed that the considered parameters are not sufficient to describe the electrical conductivity behavior.     

Thermomechanical behaviors and dielectric properties of polyaniline‐doped para‐toluene sulfonic acid/epoxy resin composites

Composites based on conductive organic/inorganic fillers dispersed in insulating matrix have been widely investigated because of their widespread applications such as electromagnetic shielding, electrostatic discharge, and sensors. In this context, novel composite materials based on epoxy resin matrix charged with polyaniline (PANI)‐doped para‐toluene sulfonic acid were elaborated. Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy were used to check the structure and the morphology of the samples. Viscoelastic behavior and thermal stability of the composites were explored by dynamic mechanical thermal analysis and thermogravimetric analysis. It was shown that the PANI particles exhibited a partial crystalline structure and were homogeneously dispersed in epoxy matrix. Consequently, this structure affected the thermal stability and viscoelastic properties of the composites. Furthermore, the dielectric and electrical properties were investigated up to 1 MHz. Measurements of dielectric properties revealed that with loading fillers in matrix, the dielectric parameters increased to high values at low frequency then decreased at values around 40 and 32 of real and imaginary parts, respectively, at 1 MHz with 15% of PANI content. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermomechanical Properties of Carbon Nanocomposites PEGDA Photopolymers

In this work, UV-curable resin poly (ethylene glycol) diacrylate (PEGDA) was reinforced with three different types of nanofillers: pristine graphene (G), multiwalled carbon nanotubes (MWNTs), and a hybrid of MWNTs and graphene 70/30 in mass ratio (Hyb). PEGDA was mixed homogenously with the nanofiller oligomer by shear mixing and then photopolymerized, affording thin, stable films. The thermomechanical properties of the afforded nanocomposites indicated the superior reinforcing ability of pristine graphene compared with MWNTs and an intermediate behavior of the hybrid.     

原位复合材料的加工性能

使用ＨＢＩＲｈｅｏｍｉｘ６１０型混合机将四种全芳香族热致液晶聚合物与热塑性树脂熔融共混，研究了混合效果，混合过程的平衡转矩与时间，温度的关系，结果显示，用该混合机可以得到均匀分散的共混体系，这些液晶聚合物具有大大低于纯聚砜的熔体粘度，将其与聚砜熔混，可使其混体系的平衡转矩比纯聚砜减小２－３倍，说明液晶聚合物是一种加工助剂，能用来改善高性能工程塑料的加工性能。