Conductive and optically non-linear polymeric langmuir-blodgett films of poly(3-dodecylthiophene)

Monolayer film formation at the air/water interface was investigated for both electrochemically and chemically prepared poly(3-dodecylthiophene) using surface pressure-molecular area isotherms. Only the electrochemically prepared polymer formed a stable monolayer, which was successfully transferred using the horizontal lifting method. The transferred Langmuir-Blodgett films were characterized by u.v.-visible spectroscopy, quartz crystal microbalance measurements, electrical conductivity measurements and femtosecond degenerate four-wave mixing studies of the third-order optical non-linearity. The third-order optical susceptibility of undoped poly(3-dodecylthiophene) was found to be χ⁽³⁾ ∼ 10⁻⁹, esu, large enough to allow the first reported observation of a degenerate four-wave mixing signal from ultrathin Langmuir-Blodgett films. In situ iodine-doping studies of u.v.-visible absorption, electrical conductivity and third-order non-linear optical susceptibility were carried out. Upon doping, the conductivity increased by more than eight orders of magnitude and the χ⁽³⁾ value decreased to within ten percent of the original value.     

Tris-fused tetrathiafulvalenes (TTF): highly conducting single-component organics and metallic charge-transfer salt

Tris-fused tetrathiafulvalene (TTF) derivatives, TTC_n-TTPY, 2,2′-bis[4,5-alkylthio-(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalenylidene] with four alkylthio chains [C_nH_2n+1S: n=3–5] are prepared and the structural and conducting properties are investigated. Crystals of the neutral molecules show very low electrical resistivity (400 Ω cm) as single-component pure organic materials. Irrespective of the alkylthio chain length, the crystal structures are so-called β″-type consisting of uniform stacks of the tris-fused TTF parts. Iodine-doped TTC₃-TTPY exhibits metallic conductivity down to liquid helium temperature.     

电活性聚合物的研究进展

电活性聚合物(Electroactive Polymer,EAP)是一种智能材料,具有特殊的电性能和机械性能.本文综述了不同类型EAP材料的国内外研究现状,并分析了材料产生电活性的原因.还介绍了EAP材料的应用领域和发展前景.目前,电活性聚合物的应用还处于尝试阶段,但是,其独特的性能决定了这种材料具有不可估量的应用前景.     

Synthesis,electrical properties and crystal structure of a new et-based charge-transfer salt containing binuclear polychloride complex anion

A new charge-transfer salt containing hexachlorodicuprate (II) binuclear polychloride complex counter anions, ET₂Cu₂Cl₆ (ET = BEDT-TTF = bis (ethylenedithio)-tetrathiafulvalene), was prepared. The room-temperature d.c. conductivity and relative resistance temperature dependence of the salt from room temperature down to 77 K along the longest crystal growth direction are reported. The crystal structure is determined by the X-ray diffraction method at room temperature. It belongs to the triclinicpl space group with crystallographic parameters of a = 11.379(4), b= 16.353(4), c = 9.054(4) A, α = 90.33(3), β= 100.69(3), γ= 100.06(2) °, V= 1628(1) A³, Z = 2, d_c = 2.261 g cm⁻³, λ (Mo Kα) = 0.710 69 A, μ = 28.45 cm⁻¹, F₀₀₀ = 1104.00 and final R = 0.043, R_w = 0.057 for 2331 observed reflections. The structure consists of isolated ET stacks and the binuclear polychloride complex dianion (Cu₂Cl₆)²⁻ sheets. In the donor stack, significantly short S···S contacts are observed.     

Suppression of the emeraldine base-to-emeraldine salt transition in ultra-thin films of polyaniline

Electronic absorption spectra of thin films of polyaniline (emeraldine base (EB) and emeraldine salt (ES)) prepared by adsorption at the solid/liquid interface and by casting from dimethylformamid and dimethyl sulfoxide solutions were investigated. Prepared by the same technique and using the same solution, the films however demonstrated divergence in their absorption spectra, depending on the film thickness. The benzenoid-to-quinoid excitonic transition in the EB was blue shifted as the film thickness was decreased. In films exposed to equal levels of acid, thicker films showed more pronounced spectral features of the ES. Spontaneous suppression of the protonation features was found in spectra of adsorbed films of ES as compared to those of a solution from which the film was adsorbed. Also, the protonation features in cast films of ES were weakened as the film thickness was decreased. Possible mechanisms responsible for this phenomenon are discussed.     

Two-photon excited states in charge-transfer type conjugated polymers

We have investigated two-photon excited states of charge-transfer (CT) conjugated copolymers, poly(aryleneethynylene) (PAE) and poly(thiophene-alt-thiazole) (PThTz), using two-photon absorption and electroabsorption methods. The fitting analysis of the experimental spectra reveals that the two-photon excited states are located 0.5–0.6 eV above the one-photon excited states. These results are compared with nonlinear optical spectra of another CT polymer and a non-CT polymer.     

The electrochemical study of corrosion resistance of silane-based hybrid films doped with rare earth salt on aluminum alloy

采用溶胶-凝胶法, 以γ-环氧丙氧丙基三甲氧基硅烷(γ-GPTMS)和正硅酸乙酯 (TEOS)为前驱体, 在2A12铝合金表面制备了稀土铈盐(Ce(NO3)3)掺杂的有机－无机杂化膜, 研究了铈盐掺杂浓度和涂层固化温度等工艺条件. 通过极化曲线和电化学阻抗谱(EIS), 比较了掺杂与未掺杂有机－无机硅烷杂化膜、铬酸盐转化膜和RE转化膜在3.5%NaCl (质量分数)溶液中的耐腐蚀性能. 测试结果均表明, 铈盐掺杂硅烷杂化膜的极化电阻比掺杂前增大了约13倍,并显著高于铬酸盐转化膜和RE转化膜.     

Conducting polymers synthesized by dopant-induced polymerization of insulating charge-transfer crystals

Conductive polymer complexes are formed by a one-step process resulting in successive doping and dopant-induced solid-state polymerization of insulating molecular complexes involving the donor biphenyl or terphenyl and acceptors such as TCNQ (7,7,8,8-tetracyano-p-quinodimethane) and DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone). The conductor resulting from the gas-phase doping of the terphenyl/TCNQ complex with AsF₅ contains low molecular weight poly(p-phenylene) chains complexed with AsF₆^? ions. Results are consistent with the presence of neutral TCNQ molecules as ‘molecular spacers’ within the conducting phase. The solid-state reaction and resulting conducting polymer are examined using spectroscopic and diffraction techniques, as well as anisotropic conductivity measurements.     

Crystal structure and properties of charge-transfer complex of N-butylguanine and FTCNQ

Charge-transfer complex formation between N-butyl guanine and FTCNQ yielded an ionic product composed of neutral and protonated N-butyl guanines and fully ionized FTCNQ molecules in a 1:1:1 ratio. Neutral and protonated N-butyl guanines were alternately connected by complementary hydrogen-bonds to form a one-dimensional ribbon, which stacked to establish a two-dimensional cation layer. FTCNQ formed a face-to-face dimer, which was separated from adjacent dimers because of the butyl group of N-butyl guanine. This salt was an insulator, and exhibited a strong antiferromagnetic interaction within the FTCNQ dimer.     

Structure,surface topography and electrochemical properties of cast films formed by fullerenes and their compositions with salt matrices

Some properties of films based on fullerene and pyridyl substituted fullerenopyrrolidines were studied. Both direct casting and immobilizing electroactive substances in the tetraoctylammonium bromide (TOAB) or tetraphenylphosphonium bromide matrices were used for modification of the ITO electrode surface. In accordance with X-ray diffraction, pyridyl substituted fullerenopyrrolidines are amorphous, and the lamellar structure of TOAB is retained when fullerene is present in the film. The differences, which are observed in the absorption spectra of the cast coatings of the individual fullerenes or fullerenes in the TOAB matrix as compared with solution spectra testify to the electronic interaction between fullerene molecules in a solid phase. At that, the quaternary ammonium salt participates immediately in the coating self-organization. Atomic force microscopy showed that both the solution composition and addends in the C₆₀ molecules influence the film morphology. Disintegration of fullerenes in the TOAB matrix and their interaction with hydrocarbon chains of TOAB provide the hydrophobic surrounding required for reversible electrochemical reduction of fullerene on an electrode in an aqueous solution. The differences observed for C₆₀ embedded in the tetraphenylphosphonium bromide and TOAB films accentuate the role of a layered structure of the matrix for the reversible electrochemical behavior of fullerene in aqueous solution.     

The hot corrosion behaviour of HVOF sprayed MCrAlX coatings under Na2SO4 (+NaCl) salt films

The hot corrosion behaviour of two NiCoCrAlYTa and CoCrAlYSi HVOF sprayed coatings and a CoCrAlY VPS coating were investigated under laboratory conditions at 900°C using a synthetic gas atmosphere containing sulphur as an impurity. All the coatings tested showed good protection under Na₂SO₄ salt films. In the presence of NaCl in the Na₂SO₄ salt films, the corrosion rates of low Al containing coatings increased considerably but the NiCoCrAlYTa coating with higher Al content still revealed good performance. It is suggested that NaCl in the salt film causes premature failure of the protective scale and reduces the incubation period of corrosion in the coatings of lower Al content. Furthermore, it seems that the finely dispersed Al rich oxide particles in the sprayed and heat‐treated HVOF coating microstructure do not lead to internal corrosion. The experimental investigations include short‐term corrosion kinetic measurements and SEM analyses.     

Electroactive Polymer Coatings on a Modified Graphite Foil as Electrodes for Supercapacitors

Protection of Metals and Physical Chemistry of Surfaces - A method for depositing electroactive coatings based on conductive polymers on a graphite foil has been developed. The electrochemical...     

A method of draining molten salt from a salt bath

Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, p. 60, May, 1990.     

New nondecarburizing salt mixtures for medium-and high-temperature salt baths

Metal Science and Heat Treatment -     

AlCl3-assisted formation of charge-transfer complexes between polyacetylene and tetracyanoethylene,TCNE

Polyacetylene, (CH)_x, the simplest conjugated polymer, can be converted into a conducting materials (8 Ω⁻¹ cm⁻¹) by treating it with TCNE/ AlCl₃/benzene solution. An electron transfer π-complex was obtained, as shown by EPR and XPS spectroscopies.     

电沉积铁氰化镍测定多孔膜电极的电活性面积

采用电化学方法测定三维多孔膜电极的电活性有效表面积、活性体积和表面覆盖度。以三维多孔电极或沉积有过渡金属铁氰化镍半导体薄膜的三维多孔膜电极为工作电极,分别在含铁氰化钾和不含铁氰化钾的碱金属溶液中测定不同扫描速度下的循环伏安曲线,利用膜电极在不同溶液体系中氧化/还原反应的可逆特性测定其电活性有效表面积和覆盖度;同时结合计时库仑法获得三维多孔膜电极内膜的活性体积和平均膜厚。结果表明:该方法具有电化学反应响应快速、灵敏且精确度高的优点,操作简单且快捷方便,可靠性好。