Direct electrochemical generation of conducting polymer micro-rings

Self-doped polyaniline (PANI) micro-rings have been successfully generated electrochemically. The polymer forming rings were about 100 nm wide, and the ring diameter is tunable from several to dozens of micrometres depending on deferent current densities. The morphology of such nanostructured polyaniline rings was investigated and further confirmed with field-emission scanning electron microscopy (FE-SEM). Furthermore, the film was characterized using UV/visible spectroscopy and cyclic voltammetry. The bubble template formation mechanism of the micro-rings was also proposed. Such nanostructured materials synthesized electrochemically open up a new approach to surface morphology control.

Patterning thin polymer films by surface-directed dewetting and pattern transfer

The pattern evolution processes of thin polystyrene (PS) film on chemically patterned substrates during dewetting have been investigated experimentally. The substrates have patterns of self-assembly monolayers produced by microcontact printing with octadecyltrichlorosilane. Optical microscopy and atomic force microscopy images reveal that ordered micrometer scale pattern can be created by surface direct dewetting. Various pattern sizes and pattern complexities can be achieved by controlling the experimental parameters. The dewetting pattern has been transferred to form PDMS stamp for soft lithography.

Pattern formation in polymer films under the mask

This paper presents a straightforward method for patterning thin films of polymers, i.e. a prepatterned mask is used to induce self-assembly of polymers and the resulting pattern is the same as the lateral structures in the mask on a submicrometre length scale, The patterns can be formed at above T-g + 30 degreesC in a short time and the external electric field is not crucial. Electrostatic force is assumed to be the driving force for the pattern transfer. Viscous fingering and novel stress-relief lateral morphology induced under the featureless mask are also observed and the formation mechanisms are discussed.

Formation of regular hole pattern in polymer films

Ordered macroporous materials recently have attracted much attention. A method that utilizes the condensation of monodisperse water droplets on a polymer solution is proposed for the preparation of honeycomb microporous films. Our results show that it is a general method that can be used for patterning a wide range of polymers. The presence of water vapor and polymer is necessary for the formation of regular holes in films. The formation of hexagonal packing instead of other kinds of packing takes place because the hexagonal packing has the lowest free energy. The formation mechanisms of regular hole pattern and imperfections in the hexagonal packing are proposed.

Incorporation of surface-derivatized gold nanoparticles into electrochemically generated polymer films

Stable colloidal solutions of gold nanoparticles surface-derivatized with a thiol monolayer have been prepared using two-phase (water-nitrobenzene) reduction of AuCl4- by sodium borohydride in the presence of 2-mercapto-3-n-octylthiophene (MOT). This kind of surface-functionalized gold nanoparticles can be easily incorporated into the poly(3-octylthiophene) (POT) films on electrode in the process of electrochemical polymerization leading to POT-gold nanoparticle (POT-Au) composite films. Scanning probe microscopy (SPM) and X-ray photoelectric spectroscopy (XPS) have been employed to characterize the surface-derivatized particles and the resulting films. The method of incorporation of nanoparticles into polymer by surface-derivatization and in situ polymerization can also be employed to prepare many other polymer-nanoparticle compostie materials.

Preparation and properties of conducting polymer of doped polyaniline LB film

Stable monolayer of polyaniline doped with camphor sulfonic acid at the air-water interface has been obtained and has been successfully deposited by Langmuir-Blodgett technique onto CaF2 substrate. IR and UV-Vis-NIR spectra show that the doped molecules dedoped partially from the PANI backbone during the monolayer compression or deposition. Gas-sensing measurement indicates that the doped polyaniline LB film was sensitive to ethanol vapor at room temperature.

Simple preparation method of multilayer polymer films containing Pd nanoparticles

A simple route to the fabrication of multilayer films containing Pd nanoparticles is described. Following layer-by-layer assembly of PdCl42- and polycation, QPVP-Os (a quaternized poly(4-vinylpyridine) complexed with [Os(bpy)(2)Cl](2+/+)), on 4-aminobenzoic acid-modified glassy carbon electrodes, the three-dimensional Pd nanoparticle multilayer films are directly formed on electrode surfaces via electrochemical reduction of PdCl42- sandwiched between polymers. The growth of PdCl42- is easy on electrode surfaces by electrostatic interaction, and the assembly processes are monitored by cyclic voltammetry and UV-vis spectroscopy. The depth profile analyses by X-ray photoelectron spectroscopy verify the constant composition of the Pd nanoparticle multilayer films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 3-7 mn. The resulting Pd nanoparticle multilayer-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen and oxidation of hydrazine compounds in aqueous solution.

Excimer formation in uniaxially stretched polymer films

The steady-state fluorescence properties of naphthalene-labeled polymers dispersed in poly(methyl methacrylate) (PMMA) cast films were studied under tensile loadings at 80 degreesC. The labeled polymers were composed of methyl methacrylate (MMA) and 1-naphthylmethyl methacrylate (NMMA). Three of the copolymers were used in this work, and the contents of NMMA were 0.59 mol % (CP1), 22.0 mol % (CP2), and 56.7 mol % (CP3), respectively. The fluorescence spectra of the films containing CP1 and CP2were unchanged during elongation. For the film containing CP3, the excited monomer emission of naphthyl groups at around 337 nm decreased with increasing applied tensile strain. The strain enhanced the emission ascribed to the excimer of the naphthyl groups in the region of 390-420 nm. The ratio of fluorescence intensities at 400 nm and 337 mn, I-400/I-337, increased with the applied strain, which indicates that CP3 is a sensitive probe for detecting the structural changes of polymer matrices. The obtained results mean that the excimer-forming sites in the PMMA films during elongation depend both on the applied strain and the concentration of naphthyl groups in the dispersed polymer probes. (C) 2001 John Wiley & Sons, Inc.

Studies on the morphology transition of micro-crystal growth in polymer films in high vacuum and strong electrostatic field

The morphology of films of isotactic polypropylene poly (3-dodecylthiophene) and iPP/P3DDT blend formed in electrostatic fields has been investigated by using scanning electron microscope. The experiment results show that the micro-crystal morphology of polymer films was strongly dependent on electrostatic fields. It was found that the effect of the electrostatic field led to the formation of dendrite crystals aligned in the field direction, and some branches of P3DDT ruptured. However, the micro-crystals in these films grew into spherulites without electrostatic field,and have no crystal orientation.

The effect of electrostatic field on the micro-crystal morphology of polymer films

The micro-crystal morphology of the films of isotactic polypropylene (iPP), poly(3-dodecylthiophene) (P3DDT) and iPP/P3DDT blend grown in different electrostatic environments has been investigated by using scanning electron microscope. The experimental results show that the micro-crystal morphology of polymer films was strongly dependent on electrostatic field. It was found that the micro-crystal morphology of the films of iPP, P3DDT and iPP/P3DDT blend grown in the electrostatic field was in the form of dendrite crystals, in which main stems were aligned in the field direction, and some branches of P3DDT were ruptured. However, the micro-crystals of the films of iPP, P3DDT and iPP/P3DDT blend have no crystal orientation in the absence of electrostatic field. (C) 2001 Elsevier Science Ltd. All rights reserved.

Energy transfer in phase-separated luminescent polymer films

The energy transfer in a blend film of poly 3-(2-(5-chlorobenzotriazolo) ethyl) thiophene (PCSET) and polyvinylcarzole (PVK) was investigated. The UV-VIS and photoluminescence (PL) results suggest that the energy transfer from PVK to PCBET leads to the enhancement of PL emission of PCBET. The AFM and LMF results indicated that the domains of blend polymer film are of micro-meter size. (C) 2001 Elsevier Science B.V. All rights reserved.

Electrochemical investigation of DNA adsorbed on conducting polymer modified electrode

Detection of DNA is a very important task for molecular biology and biomedical field. We have investigated electrochemical behavior of double-stranded DNA and single-stranded DNA adsorbed on conducting polymer modified electrode in presence of cobalt complex. The possibility of using such electrode as gene detector is discussed.

Lithium ion conducting polymer electrolytes based on alternating maleic anhydride copolymer with oligo-oxyethylene side chains

A comb polymer with oligo-oxyethylene side chains of the type -(CH2CB2O)(12)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content, The optimum conductivity attained at 25 degrees C is in the order of 5.50 x 10(-6)Scm(-1). IR spectroscopy was used to study the cation-polymer interaction.

Research on modified electrode of conducting polymer .2. Characteristics of polypyrrole film doped with heteropolyanions

Polypyrrole film electrode with Co(W2O7)(6)(10-) and CuW12O406- ions were synthesised in aqueous solutions, The electrode possesses a good stability and cyclic voltammetric behavior in weakly acidic or near neutral solutions, The redox of CuW12O406- ion can be catalysed by the polypyrrole film, The ESR measurement of the polypyrrole film with Co(W2O7)(6)(10-) and CuW12O406- ions indicates that the heteropolyanions not only play the role of neutralizing electricity in the polypyrrole film, contrasted with the film containing NO3-, but also Interact with the polypyrrole molecular chain to form some additive compound, The additive compound affects the electric structure elf the polypyrrole film and is unstable at more positive or more negative potentials.

A NEW KIND OF CONDUCTING POLYMER POLYPYRROLE (PPY) BR- ION CHEMICAL SENSOR

The modification of conducting polymer polypyrrole(PPy) on glassy carbon(GC)by electrcchemical technique, and the study on doping effect of Br anion and electrochemical behavior of PPy film electrode were reported.A new kind of Br~- ion selective electrode has been prepared successfully.The mechanism of the electrode potential response is based on the doping effect of anion in the conducting polymer.Effect of polymerization conditions on the potential response characteristic is investigated in dtail.The PPy...