Recent progress in design of conductive polymers to improve the thermoelectric performance

Organic semiconductors,especially polymer semiconductors,have attracted extensive attention as organic thermoelectric materials due to their capabilities for flexibility,low-cost fabrication,solution processability and low thermal conductivity.However,it is challenging to obtain high-performance organic thermoelectric materials because of the low intrinsic carrier concentration of organic semiconductors.The main method to control the carrier concentration of polymers is the chemical doping process by charge transfer between polymer and dopant.Therefore,the deep understanding of doping mechanisms from the point view of chemical structure has been highly desired to overcome the bottlenecks in polymeric thermoelectrics.In this contribution,we will briefly review the recently emerging progress for discovering the structure–property relationship of organic thermoelectric materials with high performance.Highlights include some achievements about doping strategies to effectively modulate the carrier concentration,the design rules of building blocks and side chains to enhance charge transport and improve the doping efficiency.Finally,we will give our viewpoints on the challenges and opportunities in the field of polymer thermoelectric materials.

SYNTHESIS OF CONDUCTIVE POLYANILINE VIA OXIDATION BY MnO_2

A unique process of chemical oxidation polymerization of aniline using manganese dioxide (MnO2) as the oxidizing agent in an aqueous medium is described. The reaction between aniline and MnO2 follows a mechanism by which the organic monomer is oxidized while the metal oxide undergoes reductive dissolution. The effects of the amount of oxidizing agent and aniline, pH and temperature of the reactive system, type of acid on the yield and conductivity of polyaniline are discussed. The resulting polyaniline was characterized by IR and UV-Vis spectrometry. Polyaniline with a conductivity of 12.5 S/cm was obtained using 0.033 mol of aniline oxidized by 0.023 mol MnO2 in the presence of 100 mL of 2.7 mol/L HCl at 25degreesC for 4 h.

Electrochemical performance of all-solid lithium ion batteries with a polyaniline film cathode

We have prepared a high-density polyaniline（PANI） paste（50 mg/m L）, with similar physical properties to those of paints or pigments. The synthesis of PANI is confirmed by Fourier transform infrared（FT-IR） spectroscopy. The morphologies of PANI, doped PANI, and doped PANI paste are confirmed by scanning electron microscopy（SEM）. Particles of doped PANI paste are approximately 40–50 nm in diameter, with a uniform and cubic shape. The electrochemical performances of doped PANI paste using both liquid and solid polymer electrolytes have been measured by galvanostatic charge and discharge process. The cell fabricated with doped PANI paste and the solid polymer electrolyte exhibits a discharge capacity of ～87 μAh/cm2（64.0 m Ah/g） at the second cycle and～67 μAh/cm2（50.1 m Ah/g） at the 100 th cycle.

Mesoporous Structure and Photocatalytic Activity of Doped Polyanilines

Photocatalytic activity of doped polyaniline nanopowders with different molar ratio of An/O （aniline^oxidizer） has been studied in the process of photocatalytic decolorization of aqueous solutions of methylene blue. By means of scanning electron microscopy and low-temperature N2 adsorption method, it was found that doped PANI （polyaniline） nanopowders have the particles size of 30-50 nm with the specific surface area of 20-35 m2.g＂~. It was found that PANI photocatalytic activity essentially depends on molar ratio of An/O and adsorption interactions between the dye molecules and catalytic active centers on PANI surface and these interactions are greatly affected by pH of the solution 9.2. An optimum of the synergetic effect is found for an initial molar ratio of aniline to oxidizer equal to 0.8.

Antibacterial Effect of the Conducting Polyaniline

Excellent antibacterial performance of polyaniline （PAni） against Escherichia coli and Gram-positive Staphylococcus aureus microorganisms has been demonstrated under both dark and visible light conditions. The electrostatic adherence between the PAni molecules and the bacteria may play a very important role for the antibacterial reaction of the PAni. As a result of our investigation, conducting PAni and its composites/blends are believed to be useful as a new type of antibacterial agent, self-clean as well as multifunctional material for improving the human health and living environment.

Hybrid supercapacitor based on polyaniline doped with lithium salt and activated carbon electrodes

Polyaniline（PANI） nanofiber was synthesized by interfacial polymerization utilizing the interface between HC1 and CCl4. The hybrid type supercapacitors （PLi/C） based on Li-doping polyaniline and activated carbon electrode were fabricated and compared with the redox type capacitors （PLi/PLi） based on two uniformly Li-doping polyaniline electrodes. The electrochemical performances of the two types of supercapacitors were characterized in non-aqueous electrolyte. PLi/C supercapacitors have a wider effective energy storage potential range and a higher upper potential. At the same time, the PLi/C supercapacitor exhibits a specific capacity of 120.93 F/g at initial discharge and retains 80% after 500 cycles. The ohmic internal resistance （REs） of PLi/C supercapacitor is 5.0 Ω, which is smaller than that of PLi/PLi capacitor （5.5 Ω）. Moreover, it can be seen that EtgNBF4 organic solution is more suitable for using as organic electrolyte of PLi/C capacitor compared with organic solution containing LiPFr.

Charge transport in conducting polyaniline co-doped with sulfosalicylic acid and dodecylbenzoyl sulfonic acid

We prepared conducting polyaniline （PAn） co-doped with sulfosalicylic acid （SSA） and dodecylbenzoyl sultonic acid （DBSA） in micro-emulsive polymerization, and studied its charge transport behaviors based on the measurement of its electrical conductivity in the temperature range between 203 K and 298 K. The conductivity was found to increase with temperature, similar to the case in semiconductors. Analyzing the experimental data with three models, namely the charge-energy-limitedtunneling model, Kivelson model and the three-dimensional variable range hopping （3D-VRH） model demonstrated that these models all describe well the charge transport behaviors of PAn co-doped with SSA and DBSA within the mentioned temperature range. From calculation with the 3D-VRH model, the hopping distance of the conducting PAn is obviously larger than its localization length. The PAn doped with SSA and DBSA enjoys desirable crystallinity due to the co-doping of two functional sulfonic acids. The macroscopic conductivity may correspond to three-dimensional transport in the network of the bundles, and the metallic islands may be attributed to quasi-one-dimensional bundles.

Surface Structure, Spectroscopic and Photocatalytic Activity Study of Polyaniline/TiO2 Nanocomposites

PANI （polyaniline） as a promising conducting polymer and photosensitizer has been used to prepare PANI/TiO2 （polyaniline/TiO2） nanocomposite as photocatalyst. TiO2 nanoparticles with size of 5-100 nm were encapsulated by PANI via the ＂in situ＂ polymerization of aniline on the surface of TiO2 nanoparticles. IR, SEM, EPR techniques were used to characterize the mechanism of electron interaction in PANI/TiO2 nanocomposite. The resulting PANI-modified TiO2 composites exhibit significantly higher photocatalytic activity than that of neat PANI on degradation of MB （methylen blue） aqueous solution under UV irradiation.

Preparation and Properties of Polyaniline in the Presence of Trehalose

Oxidative polymerization of aniline in aqueous solution in the presence of trehalose was conducted. Fourier transform infrared spectroscopy confirmed successful preparation of polyaniline containing a trace amount of trehalose. Electron spin resonance spectroscopy revealed that electron spin concentration of the polyaniline increases with aniline/trehalose ratio in the polymerization. Scanning electron microscopy revealed that the polyaniline shows granular and porous morphology. Electrical conductivity of these polyanilines was in the order of 10-4 S/cm.

High Performance Soft Electrochemical Actuators Based on Hierarchical Conductive Polymer Ionogels

Electrochemical actuators based on conductive polymers are emerging as a strong competitive in the field of soft actuators because of their intrinsically conformable/elastic nature,low cost,low operating voltage and air-working ability.Recent development has shown that adding electroactive materials,such as CNT and graphene,can improve their actuation performance.Despite the complex material systems used,their output strains(one of the key factors)are generally lower than 1%,which limited further applications of them in multiple scenarios.Here,we report soft electrochemical actuators based on conductive polymer ionogels by embedding polyaniline particles between the PEDOT:PSS nanosheets.Results show that such a hierarchical structure not only leads to a high conductivity(1250 S/cm)but also improved electrochemical activities.At a low operating voltage of 1 V,the maximum strain of these soft actuators reaches an exceptional value of 1.5%,with a high blocking force of 1.3 mN.Using these high-performance electrochemical actuators,we demonstrate soft grippers for manipulating object and a bionic flower stimulated by an electrical signal.This work sets an important step towards enabling the enhanced performance of electrochemical actuators based on conductive polymers with designed microstructures.

ELECTROACTIVE AND NANOSTRUCTURED POLYMERS AS SCAFFOLD MATERIALS FOR NEURONAL AND CARDIAC TISSUE ENGINEERING

Conducting polymer, polyaniline （PANI）, has been studied as a novel electroactive and electrically conductive material for tissue engineering applications. The biocompatibility of the conductive polymer can be improved by （i） covalently grafting various adhesive peptides onto the surface of prefabricated conducting polymer films or into the polymer structures during the synthesis, （ii） co-electrospinning or blending with natural proteins to form conducting nanofibers or films, and （iii） preparing conducting polymers using biopolymers, such as collagen, as templates. In this paper, we mainly describe and review the approaches of covalently attaching oligopeptides to PANI and electrospinning PANI-gelatin blend nanofibers. The employment of such modified conducting polymers as substrates for enhanced cell attachment, proliferation and differentiation has been investigated with neuronal PC-12 cells and H9c2 cardiac myoblasts. For the electrospun PANI- gelatin fibers, depending on the concentrations of PANI, H9c2 cells initially displayed different morphologies on the fibrous substrates, but after one week all cultures reached confluence of similar densities and morphologies. Furthermore, we observed, that conductive PANI, when maintained in an aqueous physiologic environment, retained a significant level of electrical conductivity for at least 100 h, even though this conductivity was decreasing over time. Preliminary data show that the application of micro-current stimulates the differentiation of PC-12 cells. All the results demonstrate the potential for using PANI as an electroactive polymer in the culture of excitable cells and open the possibility of using this material as an electroactive scaffold for cardiac and/or neuronal tissue engineering applications that require biocompatibility of conductive polymers.

Study of the Conductance Characteristic of Doped Polymer by Monte Carlo Method

The conduct mechanism of the doped polymer is considered. In an asymmetrysystem composed of high polymer and doping conductive matte, chain or congeries framework will beformed between the conductive particles to improve the conductance characteristic. In thisprocession, the conductive particles interact to each other. In this paper, we describe theconductance of the doped polymer by Monte Carlo method. The results accord with the experimentsquite well. It can be concluded that there is an evident change of doped polymer from nonconductorto metal.

MOLECULAR CHAIN STRUCTURE OF DOPED POLYANILINE

The chain structure of polyaniline doped with HCl or CF_3COOH has been investigated by FTIR, solid state ^(13)CNMR, resonance laser Raman and UV-VIS spectroscopies. The results show that during the protonic acid doping, a partial redox reaction takes place between the quinone-diimine and benzene-diamine units and it leads to a long conjugate system with a certain charge distribution.

THE INVESTIGATION OF DOPING OF POLYPHENYLENE SULFIDE WITH ANTIMONY PENTACHLORIDE

I. INTRODUCTION Electrical conductive polymers have attracted considerable attention since the metallic conducting polyacetylene was reported. A relatively large number of conjugated polymers are now known which can be doped with either strong electron acceptors or donors to yield conducting complexes. The preparation of conducting polymer is usually

STUDY ON POLYANILINE FILM WITH HIGH DENSITY AND HIGH MECHANICAL STRENGTH

Free-standing film of polyaniline with excellent mechanical and electrical properties has been successfully prepared by using the solution-casting method. The results show that its tensile strength, Young's modulus and elongation at break are about 87.9 MPa, 1563.9 MPa and 10.2%, respectively. It is essential that the soluble polyaniline should be appropriately treated in some suitable organic solvents before making a free-standing film. Films having lustrous, smooth surface, high density and good flexibility can only be doped by protonic acids of small molecular sizes, such as HCl, HClO_4 and H_2SO_4, to the metallic conducting regime (σ=6.7 S/cm). Discussions have been made in terms of doping behavior essentially affecting drawability and mechanical strengths.

Low Temperature Electrical Transport Studies of the Conducting Polymer Versicon™

Thermal analysis and low temperature D.C. electrical transport measurements of the conducting polymer Versicon? were carried out between 20 K and 300 K. The material was found to be stable up to 498 K (225°C), with a glass transition at 210 K (-63°C), and a crystalline transition at 436 K (163°C). The electrical resistivity data best fitted the Fluctuation Induced Tunneling (FIT) model, suggesting that at low temperatures, the electron transport is by tunneling through thermally modulated barriers. The high temperature data best fitted the thermally activated hopping model, with an activation energy of 0.015 eV, suggesting that the thermally activated hopping may be a parallel transport process to fluctuation induced tunneling, becoming dominant at higher temperatures. From the FIT model the inter-particle distance was estimated to be 12 ?. The electrical transport results were also consistent with the assertion that Versicon? forms spherical aggregates, creating conducting pathways even in an insulating matrix.

一个综合化学实验——聚苯胺的合成

聚苯胺由于具有独特的电学、光学、良好的稳定性、低成本、易于制备和应用范围广泛等特性引起了人们的广泛关注。聚苯胺可以通过化学氧化聚合和电化学聚合来制备。本实验旨在为学生提供一种快速、实用的制备聚苯胺导电聚合物的方法,展示其广泛应用。化学氧化聚合是一种具有合成简单、快速实用、原材料成本低等优点并可以用于制备大规模的聚苯胺的方法。苯胺的化学氧化聚合是在强酸性溶液中进行的,通过添加一种氧化剂过硫酸铵引发,聚合成掺杂的聚苯胺。聚合的特征是在缓慢的诱导期间颜色变化,然后在聚合阶段由于放热反应的自加速特性使得温度突然升高。掺杂后的PANI易通过与碱反应脱掺杂成为翠绿亚胺碱,其为蓝色且不导电,翠绿亚胺碱形式的PANI可与质子酸反应被掺杂重新成为翠绿亚胺盐使其具有呈现绿色并导电,从而扩展聚苯胺的应用范围。

A Solution-Processed n-Type Conducting Polymer Without Side Chains Formed via Nonmetal-Participated Polymerization and in Situ n-Doping

Solution-processed conducting polymers(CPs)are emerging as promising multifunctional materials and are motivating the development of several electronic applications.However,there are fewer highperformance electron conduction-dominated n-type CPs than p-types.Thus,the exploration of other material designs and synthesis methods is required.Accordingly,we developed a facile metal catalystfree method by combining polymerization and in situ n-doping to produce an n-type conducting polymer,poly(benzodithiophenedione)(PBTDO).The doping procedure enabled interaction between the charged conjugated backbones and solvent,dimethyl sulfoxide,making the doped conducting polymer soluble without the assistance of side chains or surfactants.PBTDO exhibited an extremely low-lying reduction level,moderate conductivity,and good air stability with potential applications in n-type organic thermoelectric devices.Moreover,it was found that the in situ doping efficiency in the reaction was highly dependent on the energy level and backbone planarity.Doping cannot occur for polymers with a high lowest unoccupied molecular orbital level and distorted conjugated chains prevent a high doping efficiency from being obtained.This study gains deeper insight into the n-doping mechanisms of conjugated polymers,with guidance for the design of highperformance n-type CPs.

导电聚苯胺的合成、结构、性能和应用

概述了中国科学院长春应用化学研究所对导电聚苯胺合成、结构、性能和应用的研究.从合成可溶性的聚苯胺入手,阐明了聚苯胺的若干基本化学和结构问题,提出并证明了掺杂态聚苯胺的结构模型和掺杂机理;除了质子酸掺杂外,发现了聚苯胺的碘氧化掺杂、光助氧化掺杂和K+注入还原掺杂;开发了分别以环氧树脂和聚氨酯为载体的聚苯胺防腐涂料;运用掺杂剂诱导的溶解性,通过合成带聚乙二醇链的膦酸掺杂剂,实现了导电态聚苯胺的水体系加工.其中的聚苯胺树脂及防腐涂料的生产技术,已经完成中试,正在走向产业化.

高导电聚苯胺薄膜的制备及其电磁屏蔽性能的研究

随着电器制品、电子器件的商用、军事用和科学应用的迅速增长 ,产生了亟待解决的电磁干扰 (也称作电磁环境污染 )问题 ,电磁干扰屏蔽日益受到关注 .本文从聚苯胺掺杂工艺角度出发 ,通过改变掺杂剂用量和溶剂种类 ,制备出高导电的聚苯胺薄膜 ,并对其电磁屏蔽特性进行了初步的测试与理论分析 。