氨基封端苯胺五聚体的合成及紫外光谱研究

对苯胺齐聚物的研究论文始于1907年,其结构和电化学性质与聚苯胺相似,易于加工,可用于金属防腐蚀引、化学传感器及催化氧化等方面,从而成为导电高分子的又一研究热点．在苯基/氨基封端(母体)、双苯基封端和双氨基封端中,前两种齐聚物已有大量研究．后一类齐聚物虽可用作电活性聚合物的单体和环氧防腐蚀涂料的固化剂,     

改进的假高稀技术合成聚苯胺三聚体和四聚体及其紫外光谱的研究

提出了一条合成还原态的苯基封端聚苯胺齐聚物的新方法 :即苯胺二聚体的 Schiff碱或苯胺三聚体的 Schiff碱在酸性溶液中缓慢水解 ,形成聚苯胺二聚体和三聚体的盐酸盐 ,这些盐酸盐与二苯胺或 N-苯基 -对苯二胺反应 ,经苯肼还原 ,生成还原态的苯基封端的聚苯胺三聚体和四聚体 .用红外、核磁、元素分析和基底辅助激光解吸质谱对其进行了表征 ,并用紫外光谱对还原态的三聚体和四聚体的化学氧化过程进行了跟踪研究     

主链含偶氮电活性聚酰胺材料的合成与性质

社会的发展和科技的进步不断对材料提出新的要求,功能材料已经成为新的研究热点,因此设计和研究高分子材料的多功能一体化具有重要的科学和现实意义。作为功能高分子材料的一种,聚苯胺因具有原料廉价、制备简便、环境稳定性好等一系列优点,以及特殊的光学、电学、磁学性质等而成为最具应用潜力的导电高分子材料[1-4]。然而聚苯胺结构上的缺陷和不溶不熔的现象,阻碍了人们对聚苯胺的微观研究和加工应用[5,6]。苯胺齐聚物具有明确的分子结构和良好的溶解性,同时光学和电学性质与聚苯胺十分相似[7,8],基本具备了成为聚苯胺替代者的条件,仅由于缺乏良好的机械性能和环境稳定性而发展受到限制。因此我们从分子设计入手,采用氧化偶联聚合方法,将苯胺齐聚物链段和具有光致异构特性的偶氮苯基团同时引入到具有良好综合性能的聚酰胺主链中,制备出一种兼具光活性和电活性的多功能聚合物材料。     

改进的假高稀技术合成聚苯胺三聚体和四聚体及其紫外光 …

提出了一条合成还原态的苯基封端聚苯胺齐聚物的新方法：即苯胺二聚体的Ｓｃｈｉｆｆ碱或苯胺三聚体的Ｓｃｈｉｆｆ碱的酸性溶液中缓慢水解,形成聚苯胺二聚体和三聚体的盐酸盐,这些盐酸与二苯胺或Ｎ－苯基－对苯二胺反应,经苯肼还原,生成还原态的苯基封 聚苯胺三聚体和四聚体。用红外、核磁、元素分析和基底辅助激光解吸质谱对其进行了表征,并用紫外光谱对还原态的三聚体和四聚体化学氧化过程进行敢跟踪研究。     

苯胺齐聚物对聚苯胺微纳米形貌形成的影响

聚苯胺是一种具有优异性能的导电高分子材料,在传感器、防腐、电容器、生物等领域有着广泛的应用前景。化学氧化聚合法是制备聚苯胺的常用方法。苯胺齐聚化是苯胺化学氧化聚合过程中的重要一步,不同条件下生成的齐聚物化学结构及其自组装方式的差异会导致最终聚苯胺的形貌迥异。本文结合目前人们较为认同的聚苯胺微纳米结构形成机理,基于产物形貌分类,综述了在化学氧化过程中的苯胺齐聚化反应和苯胺齐聚物自组装引导聚苯胺微纳米结构的形成,讨论了目前研究中的存在的问题并对今后研究方向进行了展望。     

聚苯胺/尼龙-11共混导电纤维的形态

七十年代后期由于聚乙炔的发现而迅速产生了以共轭高分子为基础的导电高分子学科 ,聚苯胺 (ＰＡｎ)也于 1 984年被ＭａｃＤｉａｒｍｉｄ等重新开发[1 ] .相对于其它共轭高分子而言 ,聚苯胺原料易得、合成简单 ,具有较高的电导率和潜在的溶液、熔融加工可能性 ,同时还有良好的环境稳定性[2～ 5] .以导电高分子为导电剂的导电纤维有其独特的优点 .与颗粒状填料为导电剂不同 ,导电高分子在纺丝拉伸过程中会产生大分子取向 ,形成更多的导电通道 ,纤维的导电性能得到提高 ,导电阈值较小 .因此 ,研究导电组分在材料中的形态分布对研制导电共混复合…     

聚苯胺膜电极在苯胺单体聚合反应中的电催化性能

自从第一个导电高聚物掺碘的聚乙炔问世以来［1］,人们又陆续开发研制了聚 苯胺(PAn)、聚吡咯和聚噻吩等导电高分子材料. 在众多的导电高分子材料中,聚苯胺以其原 料廉价易得,制备方法简便,导电性能优良,耐高温及抗氧化性能良好等优点而成为最具应用 前景的品种之一. 迄今为止,有关聚苯胺的链结构,掺杂反应,以及导电机理等基础理论方面 的研究已有大量的文献和综述报道［2～6］. 这些基础理论的研究为其应用研究奠定 了坚实的基础. 早在60年代,人们就发现,聚苯胺对氧化亚氮分解及丁二烯异构化反应具有独 特的催化作用;同时,聚苯胺具有超出几何表面的活性表面,故可对某些反应具有选择性的催 化作用. 因此,人们开始研究聚苯胺膜电极对某些电极反应的电催化性能［7～12］. 我国科学工作者在这一领域也做了许多有益的工作,如董绍俊等［13］研究了聚苯胺 膜修饰电极对抗坏血酸的电催化氧化,罗维忠等［14］研究了聚苯胺膜电极对Fe(Ⅱ) 和Sb(Ⅲ)的电催化作用. 本文主要讨论了扫描速度、苯胺单体浓度及温度对聚苯胺膜电极在 苯胺单体聚合过程中电催化性能的影响,为利用聚苯胺处理含苯胺废水提供了一定的理论依 据.     

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.     

聚苯胺的“绿色”合成

以硫酸铁为氧化剂 ,用化学法合成了聚苯胺。在不同浓度的硫酸溶液中 ,苯胺的现场可见光谱表明 ,72 0nm处的吸收峰首先形成 ,它的吸收度随反应时间而增加 ;然后 52 0nm的吸收峰慢慢形成。 72 0nm的聚苯胺在水溶液中具有低的溶解度 ,它的溶解度与苯胺聚合时所用酸的浓度有关。然而 ,52 0nm的聚苯胺能完全溶于水中。具有深色的聚苯胺溶液造成环境的污染。聚苯胺的红外光谱和循环伏安图受使用在苯胺电化学聚合中的硫酸浓度的影响。“绿色”合成聚苯胺的最佳条件是溶液的组成为 0 2mol·dm-3 苯胺、0 1mol·dm-3 硫酸铁和 0 2mol·dm-3 硫酸 ,以及温度控制在 1 5℃以下     

刚性环状低聚物的二维有序单分子膜结构

近十年来 ,为了解决耐高温高分子材料加工温度高、熔体粘度大等问题 ,材料学家们研制和开发了一系列刚性环状齐聚物 ,如环状聚芳醚酮[1] 、环状聚芳醚砜[2 ] 和环状聚苯硫醚[3] 等 .但早期人们主要把含有刚性链段的环状齐聚物 (RCO)作为结构材料研究 .1 993年 ,Miyashita[4 ] 等发现 ,含有近似刚性的酰胺键的手性环状二苯胺低聚物具有与经典 LB分子相似的双亲性 ,可以获得手性 LB膜 .近来我们合成了一系列直径可控、含有不同活性功能基团的 RCO.RCO是一类潜力巨大的有机纳米功能材料 ,其具有以下性质 :(1 )纳米空穴直径稳定且可控 ;(2…     

Reverse selectivity in m-CPBA oxidation of oligothiophenes to sulfones

Oligothiophene sulfones of up to six rings can be conveniently prepared by the direct oxidation of butyl-substituted thiophene oligomers with m-CPBA in dichloromethane. Reverse selectivity of oxidized rings is observed relative to previously reported systems without beta-substitution. The selectivity in the trimer and hexamer is confirmed with single-crystal X-ray structure data. The sulfones possess red-shifted absorptions and increased electron affinities relative to the parent oligomers.     

Electrochemistry of conductive polymers 40. Earlier phases of aniline polymerization studied by Fourier transform electrochemical impedance spectroscopy

Earlier stages of aniline polymerization have been studied by Fourier transform electrochemical impedance spectroscopy (FTEIS) experiments. Initial oxidation of aniline leads to the formation of a thin layer passivating the electrode surface, which is depassivated upon a further increase in potential and mediates a further electron transfer from aniline to the electrode. The charge-transfer resistance was first shown to decrease upon increasing the potential, which leads to the inductive behavior upon further increase in the overpotential. The oligomer-polymer film thus formed was shown to undergo a transition from its passive state to neutral oligomer-polymer molecules via a conducting state; its oxidation was then observed during the anodic scan. It is this transition to the conductive states that leads to the propagation of the conductive zone throughout the nonconductive film, leading to further growth of polyaniline, as was clearly shown by the FTEIS measurements.     

Electrochemically modulated permeability of poly(aniline) and composite poly(aniline)-poly(styrenesulfonate) membranes

The influence of oxidation state on the permeability of several probe molecules through conducting polymer membranes comprising composites of poly(aniline) and poly(styrenesulfonate) was examined in aqueous solution. Pure poly(aniline) membranes displayed a characteristic increase in permeability between reduced and half-oxidized states for neutrally charged phenol and negatively charged 4-hydroxybenzenesulfonate. In contrast, positively charged pyridine experienced decreased permeability through the membrane when poly(aniline) was switched from the reduced to the half-oxidized state. This behavior can be explained by a combination of oxidation-induced film swelling and the anion-exchange character of the positively charged membrane. The membrane composition was modified to include a fixed negative charge by the addition of poly(styrenesulfonate) during synthesis. The incorporation of this negatively charged component introduced cation-exchange character to the film and substantially reduced membrane permeability to 4-hydroxybenzenesulfonate in both oxidation states. In addition, increasing the fraction of poly(styrenesulfonate) in the membrane served to decrease film permeability for all species because of a densification of the membrane. This work demonstrates how both film composition and oxidation state can be used to tune the permeability of conducting polymer membranes.     

Electrochemical oxidation and protein adduct formation of aniline: a liquid chromatography/mass spectrometry study

Historically, skin sensitization tests are typically based on in vivo animal tests. However, for substances used in cosmetic products, these tests have to be replaced according to the European Commission regulation no. 1223/2009. Modification of skin proteins by electrophilic chemicals is a key process associated with the induction of skin sensitization. The present study investigates the capabilities of a purely instrumental setup to determine the potential of commonly used non-electrophilic chemicals to cause skin sensitization by the generation of electrophilic species from the parent compound. In this work, the electrophiles were generated by the electrochemical oxidation of aniline, a basic industrial chemical which may also be released from azo dyes in cosmetics. The compound is a known sensitizer and was oxidized in an electrochemical thin-layer cell which was coupled online to electrospray ionization–mass spectrometry. The electrochemical oxidation was performed on a boron-doped diamond working electrode, which is able to generate hydroxyl radicals in aqueous solutions at high potentials. Without any pretreatment, the oxidation products were identified by electrospray ionization/time-of-flight mass spectrometry (ESI-ToF-MS) using their exact masses. A mass voltammogram was generated by plotting the obtained mass spectra against the applied potential. Oligomerization states with up to six monomeric units in different redox states of aniline were observed using this setup. This approach was extended to generate adducts between the oxidation products of aniline and the tripeptide glutathione. Two adducts were identified with this trapping experiment. Protein modification was carried out subsequently: Aniline was oxidized at a constant potential and was allowed to react with β-lactoglobulin A (β-LGA) or human serum albumin (HSA), respectively. The generated adducts were analyzed by liquid chromatography coupled to ESI-ToF-MS. For both β-LGA and HSA, aniline adducts were successfully generated and identified.     

Absolute molecular weight of polyaniline

The absolute molecular weight of polyaniline in the pernigraniline, emeraldine, and leucoemeraldine oxidation states has been measured by light scattering and the exact number of aniline repeat units determined for the first time. Using potential-time profiling to monitor the chemical oxidative polymerization of aniline using ammonium peroxydisulfate oxidant, all three oxidation states of polyaniline can be synthesized in one step and the evolution of polymer molecular weight monitored. The pernigraniline intermediate formed during the chemical oxidative polymerization of aniline increases by 17-20% when it is converted to emeraldine, which is consistent with a two-step polymerization mechanism. These findings establish a solid experimental framework to chemically synthesize block copolymers of polyaniline by using different monomers to intercept the reaction at the pernigraniline oxidation state.     

Effect of ionizing radiation on polyaniline solutions

This communication presents the optical studies associated with transition doped (metallic)-neutral (semiconductor or insulator) state for conducting polymers. Special attention is focused on the electronic properties of polyaniline. The interconversion of different oxidation states of polyanilines has been studied by chemical and radiolytic methods. The polyaniline system is described by three sets of chromophores of three different oxidation states: fully reduced leucoemeraldine base (LB), partially oxidized emeraldine base (EB), and fully oxidized pernigraniline (PB). Each oxidation state can exist in its protonated form by treatment with an acid. All members of polyaniline family are spectroscopically distinguishable. The radiolytic study presents evidence that the polyaniline can exist in a continuum of oxidation states. The highly conducting form of polymer, i.e. emeraldine salt can be converted by using ionizing radiation into leucoemeraldine salt. The leucoemeraldine base is the final product of radiolysis of emeraldine base solution. The fully oxidized form of polyaniline can also be obtained by the irradiation of EB in the presence of CCl₄ or chlorobenzene.     

pH/potential-responsive large aggregates from the spontaneous self-assembly of a triblock copolymer in water

A simple triblock copolymer, mPEG750-aniline pentamer-mPEG750, was prepared by condensation polymerization. The solubility of aniline pentamer in this kind of copolymer was improved in common solvents especially in aqueous solution, and the electroactivity of this copolymer was confirmed by UV-vis and CV in aqueous solution. When aniline pentamer was in its emeraldine state, the copolymer spontaneously self-assembled into large spheres (with diameters up to 1000 nm) in acidic aqueous solution (pH < 3), and into microspheres (with diameters of about 300 nm) in alkali aqueous solution, while the size of the aggregates decreased with the increase of pH. For reversible transition between the large spheres and microspheres under the change of the pH and potential, which changed the doping state and the oxidation state, respectively, the copolymer has potential applications in sensors, controlled drug release, and so forth.     

Synthesis and characterization of electroactive copolymer with phenyl-capped aniline tetramer in the main chain by oxidative coupling polymerization

A novel electroactive alternating copolymer, with fixed conjugated length of oligoaniline (phenyl-capped aniline tetramer) in the main chain, was successfully synthesized via oxidative coupling polymerization. The structure of the copolymer was systematically studied by Fourier-transform infrared (FTIR) spectra, NMR, elemental analysis (EA), UV-vis spectra and X-ray powder diffraction (XRD). And its electrochemical behavior was studied by cyclic voltammetry (CV) measurement. It was found that the obtained copolymer bearing phenyl-capped aniline tetramer segments had a reversible electrochemical property in the cyclic voltammetry, and the copolymer was oxidized to its emeraldine oxidation state and then to the pernigraniline oxidation state, which was same as that of polyaniline. Moreover, the thermal properties of the copolymer were evaluated by thermogravimetric analysis (TGA). The electrical conductivity of the obtained copolymer was about 1.43 × 10⁻⁷ S cm⁻¹ at room temperature.