水溶性聚合物和两亲聚合物——10.两亲聚合物PAMC_(16)S的自组装有序膜

用自组装技术在金(纯金和经阳极氧化的金)表面上获得了新型两亲聚合物PAMC_(16)S的有序膜。用接触角测试,XPS谱和电化学分析等方法对自组装膜进行了表征。根据膜表面的润湿性,金表面的自组装膜是疏水的,亲水的磺酸基团连于金表面,而疏水的碳氢链从表面伸展出。XPS实验结果支持金表面上单层膜的疏水结构。聚合物单层膜复盖的金电极起到含有针孔缺陷的阻膈型电极的作用。单层膜在法拉第反应中显示很强的吸附稳定性,说明聚合物LB膜在潜在应用中有其特有的特点。     

Electrochemical AFM on surface grafted poly(ferrocenylsilanes)

Ethylenesulfide and trimethylenesulfide end‐functionalized poly(ferrocenyldimethylsilanes) (ES‐PFS and TMS‐PFS) with different degrees of polymerization were prepared via anionic ring‐opening polymerization. Molecular characterization of ES‐PFS was carried out by using ¹H‐NMR, GPC, FTIR, and elemental analysis. Thin films of ES‐PFS were prepared by immersing gold(111) substrates into 1.0 mg/ml solutions of the polymers in toluene. The polymeric films were characterized by FTIR, XPS, and contact angle measurements. Thicknesses of the grafted films were measured by SPR. Thicknesses determined by SPR and the theoretically calculated values are in a reasonable agreement. The morphology of the films was studied by tapping mode AFM. The electrochemical behavior of the films was monitored by cyclic voltammetry (CV). CVs show two reversible redox peaks, indicating a stepwise oxidation of the iron atoms in the polymer chains. Scanning Electrochemical Force Microscopy (SEFM) allowed us to study in situ the morphological changes occurring in the film upon electrochemical oxidation or reduction. AFM images indicated that in the oxidized form the chains were stretched due to electrostatic repulsion.     

Optical and electrochemical properties of poly(o-toluidine) multiwalled carbon nanotubes composite Langmuir-Schaefer films

Conducting poly(o-toluidine) (POT) with multiwalled carbon nanotubes (MWNTs) nanocomposite (POT-MWNTs) was synthesized by oxidative polymerization. Chloroform solutions of the material were used for the optical characterizations by means of UV-visible spectroscopy and for the fabrication of Langmuir-Schaefer (LS) films. LS films were fabricated at the air-liquid interface by using 0.1 M HCl aqueous solution as the subphase to study the electrochemical properties of the nanocomposite by means of cyclic voltammetry and photoelectrochemical techniques. The optical characterizations gave proof that the presence of MWNTs inside the polymeric matrix produced no change in the (pi-pi*) transition of POT structure, indicating that the polymeric chains were simply wrapped around and not doped by MWNTs. The electrochemical investigations highlighted significant changes in the redox properties of POT-MWNTs LS films with respect to pure POT. The cyclic voltammetric study also revealed high electrochemical stability, confirmed by the estimation of the diffusion coefficient and the photoelectrochemical response of the nanocomposite LS films. This characteristic turned out to be more evident than that obtained in our earlier studied poly(o-anisidine)-MWNTs (POAS-MWNTs) system.     

Hybrid organic/inorganic films of conducting polymers modified with phthalocyanines. II. EIS studies and film characterization

Conducting polymers were modified with Cu-phthalocyanine or Co-phthalocyanine embedded in a sol–gel matrix. The resulting films were characterized using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. Electrochemical impedance spectroscopy data showed that the application of the sol–gel layer to the conductive polymer caused a noticeable increase in the impedance of the film across the frequency ranges studied. The hydrophobic character of the film was greatly influenced by the sol–gel and caused an increase in its capacitance. A modified ‘Randles’ equivalent cell was used to correlate the electrochemical parameters of the films. Elemental analysis and infrared data confirmed the presence of the phthalocyanine moieties in the film and the empirical formula of the film was estimated. The surface morphology of the sol–gel-modified conducting polymer was distinctly amorphous compared to the poly(3-methyl thiophene).     

Effect of relative positions of substituents on the mechanism of oxidative coupling of isomeric naphthylaminosulfonic acids

We have investigated the electrochemical behavior of isomeric naphthylaminosulfonic acids in a 0.5 mole/liter sulfuric acid solution on a Pt electrode and the synthesis conditions for polymeric films based on these acids. We have established the electrochemical parameters and we propose a mechanism for anodic oxidation of naphthylaminosulfonic acids. L’viv Polytechnic State University, 12 S. Bandery St., 290646 L’vov-13, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 22–26, January–February, 1997.     

Surface characterization of 3-glycidoxypropyltrimethoxysilane films on silicon-based substrates

Silane coupling agents are commonly used to activate surfaces for subsequent immobilization of biomolecules. The homogeneity and surface morphology of silane films is important for controlling the structural order of immobilized single-stranded DNA probes based on oligonucleotides. The surfaces of silicon wafers and glass slides with covalently attached 3-glycidoxypropyltrimethoxysilane (GOPS) have been characterized by using angularly dependent X-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (ToF–SIMS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and monochromatic and spectroscopic ellipsometry. XPS and ToF–SIMS data provided evidence of complete surface coverage by GOPS. Data from angularly resolved XPS and ellipsometry methods suggested that the GOPS films were of monolayer thickness. AFM and SEM data indicated the presence of films that consisted of nodules approximately 50–100 nm in diameter. Modeling suggested that the nodules may lead to a nanoscale structural morphology that might influence the hybridization kinetics and thermodynamics of immobilized oligonucleotides.     

Electrochemically formed fullerene-based polymeric films

The recent results of investigations involving the electrochemical formation of polymers containing fullerenes and studies of their properties and applications are critically reviewed. From a structural point of view, these polymers can be divided into four main categories including (1) polymers with fullerenes physically incorporated into the foreign polymeric network without forming covalent bonds, (2) fullerene homopolymers formed via [2+2] cycloaddition, (3) “pearl necklace” polymers with fullerenes mutually linked covalently to form polymer chains, and (4) “charm bracelet” polymers containing pendant fullerene substituents. The methods of electrochemical polymerization of these systems are described and assessed. The structural features and properties of the electrochemically prepared polymers and their chemically synthesized analogs are compared. Polymer films containing fullerenes are electroactive in the negative potential range due to electroreduction of the fullerene moieties. Related films made with fullerenes derivatized with electron-donating moieties as building blocks are electroactive in both the negative and positive potential range. These can be regarded as “double cables” as they exhibit both p- and n-doping properties. Fullerene-based polymers may find numerous applications. For instance, they can be used as charge-storage and energy-converting materials for batteries and photoactive units of photovoltaic cell devices, respectively. They can be also used as substrates for electrochemical sensors and biosensors. Films of the C₆₀/Pt and C₆₀/Pd polymers containing metallic nano-particles of platinum and palladium, respectively, effectively catalyze the hydrogenation of olefins and acetylenes. Laser ablation of electrochemically formed C₆₀/M and C₇₀/M polymer films (M=Pt or Ir) results in fragmentation of the fullerenes leading to the formation of hetero-fullerenes, such as [C₅₉M]⁺ and [C₆₉M]⁺.Dedicated to Professor Dr. Alan M. Bond on the occasion of his 60th birthday.     

Surface (XPS,SIMS) chemical investigation on poly(pyrrole‐3‐acetic acid) films electrosynthesized on Ti and TiAlV substrates for the development of new bioactive substrates

Electropolymerization of pyrrole‐3‐acetic acid was performed by cyclic voltammetry on titanium and Ti90Al6V4 substrates with the aim of developing a multilayer structure for applications in advanced biomaterials. The polymeric films obtained were characterized by both XPS and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Information on the poly(pyrrole‐3‐acetic acid) (PPy‐3‐acetic) surface structure was achieved by a detailed XPS analysis of C 1s and N 1s signals. The number of COOH groups was quantified by XPS coupled to a chemical derivatization reaction in which esterification with trifluoroethanol was exploited so that the presence of fluorine (or the CF₃ component in C 1s spectra) could be used as a marker for COOH groups. As a result, it was found that more than 90% of the monomer units along PPy‐3‐acetic chains bear carboxylic functionalities, of which 60% are protonated and 40% are present as carboxylate groups. Some decarboxylation occurs with film ageing. The PPy‐3‐acetic films were also investigated by ToF‐SIMS in the negative ion mode, thus obtaining, for the first time, interesting information on the structure of the top surface layers of a polymer belonging to the polypyrrole family. In particular, clusters of peaks related to PPy‐3‐acetic oligomers were detected and the decarboxylation phenomenon on top of the polymer surface was confirmed. Copyright © 2005 John Wiley & Sons, Ltd.     

The role of mild TEMPO–NaBr–NaClO oxidation on the wet adhesion of regenerated cellulose membranes with polyvinylamine

X-ray Photoelectron Spectroscopy (XPS) was used to characterize the functional groups present on regenerated cellulose films after mild oxidation with TEMPO–NaBr–NaClO and the results were correlated with the adhesion forces holding together two wet cellulose films laminated with a thin (i.e. less than 10 mg/m²) layer of polyvinylamine (PVAm). There was no correlation between adhesion and carboxyl content, whereas wet adhesion was proportional to the total content of aldehyde and hemiacetal groups on the cellulose. It is proposed that aldehyde groups react with neighboring cellulose chains to form hemiacetals which serve as crosslinks strengthening the cellulose surface. The hemiacetals can also be attacked by primary amines to give imine and aminal covalent linkages to the PVAm adhesive layer.     

Poly(vinylferrocenium) perchlorate–polyaniline composite film-coated electrode for amperometric determination of hydroquinone

Poly(vinylferrocenium) perchlorate–polyaniline (PVF⁺–PANI) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and aniline monomer. PVF⁺ polymer in the composite film was used as an electron transfer mediator. The composite coating showed significant electrochemical activity towards hydroquinone (HQ) at pH 4, with high sensitivity and a wide linearity range. The interaction of HQ with PVF⁺ and PANI homopolymer films was investigated electrochemically and spectroscopically. HQ molecules are accumulated on the electrode surface due to trapping by both polymers in the composite film and then oxidized catalytically by PANI. The most significant contribution of PVF⁺ polymer is that it facilitates electron transfer in the composite film. The linear response range was found to be between 1.60 × 10⁻⁴ mM and 115 mM (R ² = 0.999) at 0.45 V vs saturated calomel electrode. The limit of detection (LOD) was 4.94 × 10⁻⁵ mM.     

聚呲咯的研究

本文研究了不同电化学氧化聚合条件下所得聚吡咯的红外光谱,X射线光电子能谱、元素分析、X射线衍射图及扫描电子显微镜图等。对聚吡咯的电导性、电导率的依赖性、化学结构及结晶性等进行了讨论。     

A new Solid-State pH Sensor Based on a Platinum Nanoparticle Surface Coated with Poly(quinoxaline), and its Application

A new solid-state pH sensor has been constructed based on a poly 3,4-dihydro-2-hydoxyquinoxaline (HOQ) thin film electrochemically deposited onto a Pt disc electrode whose surface had previously been modified with Pt nanoparticles by electrochemical depositing from HPtCl₆–H₂SO₄ solution at −0.2 V. The poly HOQ film was deposited from HAc–NaAc solution by cycling the potential between 0.4 V and 1.1 V. The typical response of the pH sensor and its reversibility was investigated. The emf signal was linear over the pH range of 2 to 13 with a super-Nernstian slope of 63.3 mV/pH unit. The response time ranged from several seconds at a pH of around 7 up to 2.5 min at pH 13. The performance of the pH sensor was examined by measuring organic acid, amine and amino groups on the surface of composite nanomaterial samples and sat isfactory results were obtained.     

Anion receptor-coated separator for lithium-ion polymer battery

Anion receptor-coated separators were prepared by coating poly(ethylene glycol) borate ester (PEGB) as an anion receptor and poly(vinyl acetate) (PVAc) as a good adhesive material towards electrodes onto microporous polyethylene (PE) separators. Gel polymer electrolytes were fabricated by soaking them in an liquid electrolyte, 1 M LiPF₆ in EC/DEC/PC (30/65/5, wt.%). As the weight ratio of PEGB to PVAc in a coating layer increased, gel polymer electrolytes showed higher cationic conductivity and electrochemical stability. The cationic conductivity and electrochemical stability of the gel polymer electrolyte based on coated separator with PVAc/PEGB (2/5, weight ratio) could reach 2.8 × 10^–4 S cm^–1 and 4.8 V, respectively. Lithium-ion polymer cells (LiCoO₂/graphite) based on gel polymer electrolytes with and without PEGB were assembled, and their electrochemical performances were evaluated.     

Preparation and characterization of poly(phthalazinone ether ketone)/SiO<Subscript>2</Subscript> hybrid composite thin films with low friction coefficient

Organic–inorganic poly(phthalazinone ether ketone) (PPEK)/SiO₂ hybrid composite thin films were prepared by the dip-coating method on pre-cleaned glass substrates. The covalent bonds between organic and inorganic phases were introduced by an in-situ O-acylation reaction of isocyanatopropyltriethoxysilane (ICPTES) with the borohydride-reduced PPEK forming a polymer bearing triethoxysilyl groups. Theses groups were subsequently hydrolyzed with tetraethoxysilane (TEOS) and allowed to form a network via a sol–gel process. The polymer hybrid composite exhibited good thermal stability and a higher glass transition temperature as compared with the pure resin. Atomic force microscope, water contact angle measurement and scanning electron microscope were used to characterize the polymer hybrid thin films. The tribological experiment showed that the films have very low friction coefficient (about 0.1) and good anti-wear properties, without failure even after sliding for 18,000 s under modest loads. The improved tribological properties of the modified substrate were attributed to good adherence of PPEK/SiO₂ hybrid films on the substrate and synergy of both PPEK matrix and silica particles.     

Electrosynthesis and characterization of poly(3-methylthiophene) on different substrates

 We report on the study of the electropolymerization of 3-methylthiophene onto Pt, p-Si and indium-tin oxide deposited on polyester using quartz crystal microgravimetry, electrochemical and spectroelectrochemical measurements. We observe that potential variation during the galvanostatic electrodeposition is correlated with the nucleation process. The mass variation of poly(3-methylthiophene) is linear with the amount of the electrochemical charge whereas the absorbance variation curve shows two distinct slopes. The latter result has been explained in terms of conjugation length variation during polymer growth. Scanning electron microscopy analysis allowed the detection of morphological changes from a dense and compact structure to an open morphology when the poly(3-methylthiophene) film thickness increases. The roughness of the films did not change considerably with the substrate, as observed by atomic force microscopy. Absorption and photocurrent spectra at different film thicknesses show a shift of the peaks to lower wavelengths when the thickness increased, thus confirming the decrease of mean conjugation length in thicker films. Received: 1 September 1998 / Accepted: 11 November 1998     

Synthesis of the perovskite ceramic Li3xLa2/3–xTiO3 by a chemical solution route using a triblock copolymer surfactant

The synthesis of the perovskite Li_3xLa_2/3–x□_1/3–2xTiO₃ by a chemical solution route, using a triblock copolymer surfactant, PEO_n–PPO_m–PEO_n, is described. This titanate is a non-hygroscopic fast lithium conductor and therefore is a good candidate for electrochemical applications. It is generally prepared by a conventional solid-state reaction (SSR) method. However this synthesis method does not allow the preparation of nanopowders or the formation of thin films. For these special purposes, synthesis by a chemical solution route, with the formation of a polymeric precursor during synthesis, has been investigated. By using the above-mentioned non-ionic surfactant, the preparation of nanopowders of complex oxides can be done. Furthermore, this way of synthesis leads to the formation of an intermediate polymeric precursor which can be easily spread on substrates to obtain films. We show that the formation of a pure phase of the perovskite Li_3xLa_2/3–x□_1/3–2xTiO₃ is highly dependent on the synthesis conditions, namely the presence of water in the solvent, the EO/metal ratio, the Li⁺ content in the precursor and the calcination temperature. The influence of these parameters on the microstructure of the oxide is studied by X-ray diffraction, scanning electron microscopy and granulometry. A powder of Li_3xLa_2/3–x□_1/3–2xTiO₃ (x = 0.10), with an average particles size of 200 nm, has been obtained. The ionic conductivity of this oxide is the same as the one obtained with oxide prepared by SSR (a bulk conductivity of 1.4 × 10⁻³ S/cm at 37 °C). The ceramic obtained from this powder after sintering at 1,150 °C shows a good pH response. This material can then be used as a sensitive membrane in a potentiometric pH sensor. The presence of hydrophobic PPO groups in the polymer precursor allowed preparing films of Li_3xLa_2/3–x□_1/3–2xTiO₃ with a good adherence on Pt substrate. This kind of synthesis is then very promising to prepare micro pH sensors.     

Composite electrodes consisting Pt nano-particles and poly (aminophenols) film on pre-treated aluminum substrate as electrocatalysts for methanol oxidation

Electrochemically platinum plated aluminum (Al/Pt) was used as an electrode substrate for the electropolymerization of aminophenols and fabrication of composite electrodes based on platinum nano-particles. The poly(o-aminophenol) (PoAP), poly(m-aminophenol) (PmAP), and poly(p-aminophenol) (PpAP) were synthesized on the Al/Pt electrode, and further modification was performed by deposition of platinum nano-particles onto polymer matrixes. The electrochemical and morphological characteristic of the composed electrodes were carried out by cyclic voltammetry and scanning electron microscopy, respectively. The electrocatalytic oxidation of methanol on the composite electrodes was studied by cyclic voltammetry in 0.1 M sulfuric acid as supporting electrolyte. It was found that the Al/Pt/PoAP electrode incorporated Pt nano-particles (Al/Pt/PoAP/Pt) exhibits a higher electrocatalytic activity for the oxidation of methanol than the Al/Pt/PmAP/Pt and Al/Pt/PpAP/Pt electrodes. On the other hand, a higher catalytic current for methanol oxidation was found on the Al/Pt/PoAP/Pt electrode in comparison to bulk Pt and Al–Pt (Al with 0.2 mg cm⁻² of Pt particles) electrodes. The effects of various parameters such as thickness of the polymer film, concentration of the monomer, Pt loading method and the Pt amounts, concentration of the methanol, and the medium temperature were studied on the electrooxidation of methanol. The long-term stability of the modified electrode has also been investigated.     

Polymer films on electrodes: Part II. Film structure and mechanism of electron transfer with electrodeposited poly(vinylferrocene)

The structure and properties of electrodeposited poly(vinylferrocene) (PVF) films on platinum electrodes (PVF/Pt) were examined by electron microscopy, X-ray photoelectron spectroscopy, various electrochemical techniques and measurements of the film resistance. The data were consistent with a mechanism in which the polymer films are permeable to dis-solved reactants. A theoretical treatment of this situation for chronoamperometry is presented. The oxidation and reduction of a variety of dissolved reactants with redox potentials far removed from that of the PVF/PVF⁺ system at PVF/Pt occurred by diffusion of the electroactive species through the polymer film and subsequent reaction at the platinum surface.     

Hybrid organic/inorganic films of conducting polymers modified with phthalocyanines. I—Film preparation and voltammetric studies

Conducting polymers were deposited on the surface of platinum and glassy carbon electrodes. The monomers used were N-methyl pyrrole and 3-methyl thiophene. The electrochemical synthesis of the polymer was achieved using constant applied potential or cyclic polarization techniques in acetonitrile as a solvent and tetra-alkyl ammonium salts as supporting electrolyte. The resulting conducting polymeric film was modified with an inorganic metal complex, namely, Cu–phthalocyanine or Co–phthalocyanine. Two different approaches were adopted for the modification: (1) the first was to directly apply the metal–phthalocyanine layer on the surface of the polymer, and (2) the second was by the inclusion of the metal–phthalocyanine in a sol–gel matrix that was in turn applied to the conducting polymer film. In the first part of this work, we studied the effect of changing the type of polymer matrix and the central metal of the inorganic complex on the electrochemical behavior of the resulting film. We also found that changing the method of metal–phthalocyanine application to the polymer film affected the electrochemical response and kinetics at the electrode surface. The new electrode was tested for the reduction of hydrogen peroxide and showed better conversion efficiency compared to conventional surfaces, which suggests its use in fuel cell applications.     

The effect of the nature of the dopant on the sensor response of poly(3-methylthiophene) films

The effect of the nature of the dopant on the response of a sensor array based on films of poly(3-methylthiophene) under the influence of various organic solvents was studied. It was established that the electroconductivity of the polymer can both increase and decrease under the influence of the analytes. It was suggested that the main factors determining the magnitude of the response of poly(3-methylthiophene) are the ratio of the number of radical-cationic and dicationic states in the polymer, which depends on the nature of the dopant-anion, and also the polarity of the analyte. It was shown that the polymer has high sensitivity to chloroform vapor, which makes sensor arrays based on poly(3-methylthiophene) selective with respect to this analyte. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 331–338, November–December, 2006.