Self-assembly of aniline oligomers in aqueous medium

By dissolving branched or linear aniline oligomers in polar solvent and introducing their stock solution into an aqueous acidic medium, sheet-like as well as wire-like supramolecular structures with well-defined morphology were obtained, respectively. These oligomeric supramolecular structures were constructed via a post-synthetic precipitation process, indicating that aniline oligomers are capable of self-assembling in an aqueous medium, which is similar to the reaction medium of aniline chemical polymerization. Possible formation mechanisms of these supramolecular structures were proposed, i.e., sheet-like products were probably constructed by collapsed molecular chains of aniline oligomers with branched units through π–π stacking and hydrogen bonding, whereas formation of the wire-like products was attributed to “oriented-attachment” of collapsed molecular chains of linear aniline oligomers. The findings obtained in this study are supposed to provide useful clues for uncovering the formation mechanism of polyaniline micro-/nanostructures.     

层层自组装原位聚合聚苯胺复合膜成膜机理研究

从苯胺单体出发, 通过原位聚合、现场掺杂以及基于静电力的层层自组装制备了聚苯胺复合膜. 通过苯胺活性溶液的温度及颜色变化跟踪聚合反应进程, 同时考察不同聚合反应阶段所得聚苯胺复合膜的紫外-可见吸收, 并进一步探讨聚苯胺复合膜的成膜机理. 研究表明, 成膜机制是由聚合反应初始阶段的苯胺阳离子或苯胺阳离子自由基通过静电作用快速吸附到负电性的基片表面, 形成均匀的聚合中心, 链增长生成聚苯胺; 该聚苯胺在酸性条件下经现场掺杂显电正性, 可吸附电负性的聚苯乙烯磺酸钠(PSS), 以此循环层层组装得到多层聚苯胺复合膜.     

Molecular complexes and solvation interactions in the reaction of quinone imines with thiols

This study aims to investigate the role of complexation between reagents and the role of solvation of reagents by solvents in the kinetics of chain reactions of quinone imines with thiols. The thermodynamic characteristics of the complexation of quinone imines with thiophenol in CCl₄, chlorobenzene, and ethanol, as well as of the complexation of quinone imines and thiophenol with these solvents were calculated by quantum chemical methods (DFT calculations at the PBE/cc-pVDZ level of theory) and in terms of the additive-multiplicative model. Both approaches give consistent results. The formation of molecular complexes in quinone imine–thiphenol systems is accompanied by a 10–30 kJ mol^–1 decrease in enthalpy and has only a slight effect on the reaction mechanism.     

Self-assembly of aniline oligomers and their induced polyaniline supra-molecular structures

Aniline chemical oxidative polymerisation (COP), which produces various polyaniline (PANI) and oligoaniline supra-molecular structures, can be regarded as an in situ self-assembly process. This review provides a brief introduction to recent work on the structural characters and self-assembly behaviours of oligomeric aniline chemical oxidation products; it is focused on the relationships between the oligomeric species and morphology of the final products such as PANI nanoparticles, nanofibres/rods, nanotubes or oligoaniline nanosheets, micro/nanospheres in aniline COP systems. Several mechanisms proposed as explanations for the formation of typical supra-molecular structures are discussed in order to illustrate the roles of aniline oligomers. This article concludes with our perspectives on future work remaining to be done to uncover the formation mechanism of supra-molecular structures constructed by aniline chemical oxidation products and their controllable synthesis.     

Electrochemical oxidation of aniline in a silica sol–gel matrix

Electrochemical oxidation of aniline encapsulated in a silica solid electrolyte prepared by a sol–gel process yielded products that were dependent on the pore size. An acid-catalyzed process that used tetramethyl orthosilicate as the precursor and aniline as a dopant yielded the silica. When the aging time was limited to one day so that a mesoporous solid was obtained, the potentiodynamic oxidation of aniline at a carbon fiber electrode resulted in the formation of polyaniline. With aging times of 3–5 days, microporous silica was obtained. In this electrolyte, the formation of dimers and other oligomers was observed by cyclic voltammetry. Evidence for these products was the presence of a quasi-reversible redox couple at 0.2 V vs Ag/AgCl that was previously related to oligomeric aniline by Raman spectroscopy. The results supported the hypothesis that the pore structure of sol–gel electrolytes can influence the pathways of electrode reactions therein.     

用氧化偶联聚合法合成新型电活性聚酰胺及其结构表征

使用氧化偶联聚合的方法, 合成了一种新的电活性聚酰胺, 使其同时具有聚酰胺和聚苯胺性质. 该反应操作简便易行, 室温下即可进行. 通过红外光谱和核磁共振谱对其结构进行了表征, 用紫外-可见光谱和循环伏安法研究了氧化还原性质和电活性, 并测试了导电率.     

纳米聚苯胺及聚苯胺/金复合材料的制备与表征

以氯金酸(HAuCl4)为氧化剂,在两种不同无机酸(HCl和H2SO4)的掺杂下,通过调节反应体系中混合溶剂的醇水比例,用一步氧化苯胺聚合法成功制备了不同形貌的纳米聚苯胺及聚苯胺/金复合材料.通过扫描电子显微镜(SEM)、紫外可见吸收光谱(UV-Vis)和红外光谱(FT-IR)对产物的形貌和结构进行了表征.在此基础上,进一步讨论了聚苯胺/金复合材料可能的形成机理.     

氧化偶联聚合方法合成电活性聚芳醚酮

通过氧化偶联聚合方法成功地合成出电活性聚芳醚酮. 该反应条件温和, 操作简单, 室温下即可进行. 用红外光谱、核磁共振谱、高效凝胶渗透色谱、循环伏安、热失重、X射线衍射等技术对所合成的聚合物进行了表征, 并探讨了聚合物的性能.     

Hydroxyl-functionalized polyaniline nanospheres: tracing molecular interactions at the nanosurface via vitamin C sensing

Here, we report a synthesis of novel polyaniline nanospheres bearing mono- and bishydroxyl functional groups to trace the molecular interactions at the nanosurfaces through vitamin C sensing. Two new aniline monomers were synthesized via a tailor-made approach and polymerized to produce soluble and uniform polyaniline nanospheres. The structures of the monomers and polymers were characterized by NMR, FT-IR, and MS techniques, and the morphology of the nanomaterials was analyzed by SEM and TEM. The mechanistic aspects of the nanomaterial formations were analyzed by FT-IR and dynamic light scattering techniques. These studies revealed that the hydroxyl-functionalized monomers have strong hydrogen bonding at the monomer level and form spherical aggregates in water, which are templates for the polyaniline nanospheres 600 +/- 100 nm in size. A controlled synthesis was also carried out using aniline hydrochloride as an unsubstituted counterpart, which yields polyaniline nanofibers. WXRD analysis confirmed the presence of a sharp peak at lower angle at 2theta = 7.3 degrees ( d-spacing of 13.4 A) in hydroxyl-substituted nanospheres with respect to enhancement of solid-state ordered crystalline domains, whereas unsubstituted nanofibers were found to be highly amorphous. Vitamin C was employed as an analyte to trace the molecular interaction at the nanosphere surface and study the influence of nanosurface functionalization on the sensing ability of biomolecules. The bishydroxyl-functionalized polyaniline nanospheres were found to show efficient molecular interactions toward vitamin C, whereas nanospheres with a monohydroxyl group or unsubstituted nanofibers failed as sensing materials. In a nut shell, in the present investigation, for the first time, we have proved the importance of surface functionalization of polyaniline nanomaterial, exclusively nanospheres, using hydroxyl groups for studying the molecular interactions at the nanosurfaces with biomolecules such as vitamin C.     

Bi-hybrid coatings: polyaniline-montmorillonite filler in organic-inorganic polymer matrix

A bi-hybrid composite is represented by an organic-inorganic (O-I) filler dispersed in an O-I matrix. Polyaniline-montmorillonite, as a nanocomposite filler, was synthesised by two independent processes: (1) montmorillonite was surface-modified with a conducting polymer, polyaniline, during the in-situ oxidation of aniline or (2) montmorillonite was pre-treated with aniline, then the aniline was polymerised and the polyaniline subsequently produced penetrated the montmorillonite structure. The organic-inorganic polymer matrix was formed in two independent steps: (1) inorganic building units were formed in situ by the sol-gel process, (2) followed by organic polymeric matrix formation by polyaddition reactions of epoxy groups with amines. Polyaniline-montmorillonite filler was added to the reaction system between these two steps, i.e. when the inorganic structures of the O-I matrix have already been formed but prior to formation of the organic polymeric matrix. Two different O-I matrices were prepared from functionalised organosilicon precursors and oligomeric amines. 3-[(Glycidyloxy)propyl]trimethoxysilane reacted with α,ω-oligo(propylene oxide) diamine and diethoxy[3-(glycidyloxy)propyl]-methylsilane reacted with α,ω-oligo(propylene oxide) triamine. The resulting bi-hybrid coatings, the O-I filler dispersed in the O-I matrix, were characterised by atomic-force and optical microscopies, and also by tensile tests. The filler composition affected both the mechanical and surface properties of the coatings.     

Pyridinium chlorochromate oxidation route to polyaniline

In this work, for the first time, pyridinium chlorochromate is used as an oxidizing agent inorder to oxidize aniline to polyaniline salts via an aqueous polymerization pathway in the presence of protic acids such as sulfuric, nitric, hydrochloric and phosphoric acid. The polymer samples were characterized by infrared, electronic absorption spectral, elemental analysis, conductivity, density and water absorption measurements. The results of the polyaniline salts prepared by pyridinium chlorochromate as an oxidizing agent were compared with that of the polyaniline salt prepared by ammonium persulfate. Generally, aniline is oxidized using ammonium persulfate as an oxidizing agent, which is unstable. In this work, pyridinium chlorochromate is used to oxidize aniline to polyaniline salt and the polymerization reaction could be completed in 30 min. Copyright © 2003 John Wiley & Sons, Ltd.     

原位聚合法制备PANI/PET导电织物及其性能分析

在聚酯纤维基材及其织物表面,原位聚合形成厚度约1~2μm聚苯胺包覆层,制得聚苯胺(PANI)/聚酯(PET)导电织物.PANI层优异的导电性能使之成为有广阔发展前景的柔性电磁屏蔽材料.正交试验分析研究了苯胺单体浓度、氧化剂:苯胺摩尔比、掺杂酸浓度、反应时间对PANI包覆层外观形态、与基体结合牢度以及导电性的影响.实验表明:在经适当前处理的PET基材表面,以苯胺单体浓度为0.25mol/L、氧化剂与苯胺摩尔比为1∶1、掺杂酸浓度0.5 mol/L、反应时间60 min、反应温度为0~20℃时制备的PANI/PET导电织物方阻最小,导电性最好;掺杂酸酸性越强,导电性越好.SEM、FTIR及XRD测试表明涤纶织物表面有均匀连续的聚苯胺膜存在.分析表明聚苯胺分子链中氧化结构与还原结构含量基本相等,说明聚苯胺渗入纤维内部,使纤维无定形区面积增加,结晶度减小.     

Synthesis and properties of latex particles with polyaniline shells

Core–shell polyaniline–latex particles have been obtained via oxidative polymerization of aniline hydrochloride in the presence of charged polystyrene latex. The polymerization conditions have been determined under which polyaniline is predominantly formed on the surface of latex particles to yield closed shells. The dependence of the electrical conductivity of the resulting particles on the initial concentration of aniline hydrochloride in the polymerization medium has been studied. Stable aqueous dispersions of polyaniline–latex particles have been prepared by modifying the particles with sodium 3-mercaptopropane sulfonate.     

Synthesis of imines from nitrobenzene and TiO2 particles suspended in alcohols via semiconductor photocatalysis type B

UV irradiation on a non-aqueous suspension of titanium dioxide with nitrobenzene and different alcohols in deaerated conditions produces imines and aniline as main products. The conversion of nitrobenzene and the corresponding selectivity of imines or aniline depend on the type of alcohol used. A low conversion (3-12%) and selectivity close to 100% to imines were obtained with methyl, ethyl, or propyl alcohol. Otherwise, using i-propanol only aniline was detected with a conversion of 13%. Finally, a mixture of aniline and imines was formed employing n-butyl, n-amyl, and i-amyl alcohols with the higher conversion (∼50%).     

Preparation of hybrid film of polyaniline and organically pillared zirconium phosphate nanosheet by electrodeposition

α-Zirconium phosphate was chemically modified with 1,2-bis(dimethylchlorosilyl)ethane to graft organic chain, and then it was used as host material for inorganic nanosheet-polyaniline hybrid. The grafted α-zirconium phosphate was exfoliated in an acetonitrile solution with tetrabutylammonium salt and aniline. The electrodeposition in the presence of aniline was performed, and then it resulted in a formation of higher-order structure in which phosphate nanosheet was propped up by 1,2-bis(dimethylchlorosilyl)ethane with intrusion of polyaniline into the nanospace. The gravimetric capacitance of the α-zirconium phosphate without grafts and polyaniline hybrid film was around 194 F/g with the base on the amount of polyaniline mass. On the other hand, the α-zirconium phosphate nanosheet with grafts and polyaniline hybrid film provided larger capacitance of around 350 F/g in maximum. The nanospace formed by grafted phosphate nanosheet with 1,2-bis(dimethylchlorosilyl)ethane molecules gives increased amounts of polyaniline included and diffusion paths for ions.     

Catalytic effect of hydroxyl-containing compounds at the propagation step of the chain reaction of thiophenol with quinone imines

Russian Chemical Bulletin - Hydroxyl-containing compounds (water, methanol, and phenol) act as efficient catalysts of the chain reactions of thiophenol with quinone imines at their propagation...     

A NEW APPROACH TO ELECTROACTIVE POLYMERS VIA WELL-DEFINED OLIGOMERRS WITH FURTHER POLYMERIZABLE END-GROUPS

Among the inherent drawbacks of conducting polymers are the limited processibility, uneven polydispersity inmolecular weigh and the existence of structure defects, which become the obstacles for many electronic, optical andbiological applications that demand the materials to have well-defined structures and high chemical purity. To solve theseproblems, our research in the last decade or so has focused on the synthesis of electroactive oligomers of well-definedstructures, controllable molecular weighs, narrow or uniform polydispersity. We have developed a general strategy for thesynthesis of such oligomers based on the theory of non-classical or reactivation chain polymerization. The aniline oligomerswith minimum 4 nitrogen atoms and 3 phenylene rings exhibit similar characteristic redox behavior and electroactivity aspolyaniline. Electronic conductivity of the oligomers of 7 or 8 aniline units approaches that of polyaniline. Solubility of theoligomers is much improved over that of conventional polyaniline. Various functional groups can be introduced into theoligomers either by proper selection of starting materials or by post-synthesis modifications via common organic reactions.The functionalized oligomers undergo further polymerizations to afford a variety of new electroactive materials, includingpolyamides, polyimides, polyureas, polyurethanes, polyacrylamides and epoxy polymers. Numerous potential applications,particularly as anticorrosion materials, are discussed for the oligomers and their polymeric derivatives.     

Chemically Modified Ordered Mesoporous Carbon/Polyaniline Composites for Electrochemical Capacitors

Chemically modified ordered mesoporous carbon CMK-3 materials were prepared by means of an easy wet-oxidative method in 2 mol/L nitric acid aqueous solution. A large amount of oxygen-containing functional groups were introduced onto the CMK-3 surface. Modified CMK-3(m-CMK-3) and aniline monomer were polymerized via an in situ chemical oxidative polymerization method. Morphological characterizations of m-CMK-3/PANI (polyaniline) composites were carried out via field emission scanning electron microscopy(SEM)...     

掺杂质子酸的类型对聚苯胺结构和电导率的影响

采用化学氧化聚合法以苯胺为单体，过硫酸铵为氧化剂，在不同质子酸的水溶液中合成聚苯胺，考察质子酸对聚苯胺电性能影响，并通过傅立叶红外吸收光谱（FTIR）和紫外可见光吸收光谱（UV－vis)研究聚苯胺掺杂前后结构的变化。结果表明，龙质子酸掺杂后聚 胺具有导电性是因为其分子链上电荷离城形成了共轭结构，具有不同质子酸中生成的聚苯胺氧化程度不同；分子链共轭程度与掺杂酸对阴离子大小有关，掺杂质子酸对阴离子越大，聚苯胺分子链共轭程度越大，电导率也就越高。     

新型锂电池正极材料多硫代聚苯胺的制备和电化学性能

通过聚苯胺合成了多氯代聚苯胺以及锂电池正极材料多硫代聚苯胺,利用元素分析、红外光谱、X射线光电子能谱和扫描电镜对反应产物多氯代聚苯胺和多硫代聚苯胺进行了化学结构和形貌分析.XPS结果表明,多硫代聚苯胺没有明显的π-π^*电子离域现象.多硫代聚苯胺的主链聚苯胺对侧链S-S未发现有明显的电化学催化作用.多硫代聚苯胺的充放电曲线及其微分曲线表明,其在充放电过程中可能存在3个连续的氧化还原反应过程,在2.07V处有一个明显的放电电位平台.放电比容量在30次循环中能够维持在181-187mA.h/g之间,循环效率达到94%.