P. Passiniemi

Polyaniline/epoxy coatings with good anti-corrosion properties

We have studied polyaniline/epoxy blend coatings on mild steel in 0.6 M NaCl and 0.1 M HCl aqueous solutions with electrochemical methods. The corrosion protective performance was characterized by a permanent shift of corrosion potential by about 500 mV to the noble direction and by a decrease of five orders of magnitude in the redox current. The surface of mild steel was covered by a light gray protective layer due to the electrochemical interaction between the coating and steel. The chemical composition of the surface layer has been studied with X-ray photoelectron spectroscopy (XPS).

Counter-ion induced processibility of polyaniline: conducting melt-processible polymer blends

Summary form only given. Conducting polymer blends made by blending thermoplastic bulk polymers with Polarene/sup TM/, a proprietary conducting polyaniline composition, using conventional melt-processing techniques are reported. The percolation threshold for conductivity is observed at astonishingly low weight fractions of the conjugated conducting polyaniline indicating the formation of a unique morphology. Results on electrical and mechanical properties of these blends will be presented and discussed.

On the molecular recognition and associations between electrically conducting polyaniline and solvents

The specific interactions between sulphonic acid protonated polyaniline (PANI) and solvents are here studied both by the semiempirical AM1 method and experimentally. Phenolic solvents are shown to have a relatively large interaction with the sulphonate anions of the counterions and with the amines in PANI. In addition, a properly functionalized counterion may form cyclic associations provided that there is a steric match between the molecules concerned. This concept is called molecular recognition and it is a novel concept in the context of PANI. For example, the carbonyl group in (±)‐10‐camphor sulphonic acid (CSA) can form a hydrogen bond to the hydroxyl group of m‐cresol, whereby the phenyl ring becomes coplanar with one of the PANI rings thus enabling enhanced van der Waals interaction. This additional specific interaction agrees with our observed increased solubility with CSA doped PANI in m‐cresol, compared to its solubility in dimethyl sulphoxide or chloroform, or to tosylene sulphonic acid doped P...

Electrically conductive compositions based on processible polyanilines — PANEPOL TM

Abstract Truly melt- and solution processible electrically conductive polyaniline (PANI) compositions can be produced commercially utilizing the technology originally developed some years ago in a joint-effort between Neste Oy and UNIAX Corporation. This technology, PANIPOL TM , utilizes PANI protonated by functionalized protonic acids in combination with proprietary plasticizers. Neste has now further developed this technology and reached semi-industrial scale production capabilities. We briefly discuss some features of fusible, conductive PANIPOL TM compositions developed specifically for use in conductive products such as injection molded articles, extruded films and fibers.

Synthesis and properties of FeCl4-doped polythiophene

Abstract Electrochemically synthesized polythiophene films containing BF 4 − -anions, PT-BF 4 , have been carefully reduced and re-oxidized with FeCl 4 -anions to obtain highly conducting PT-FeCl 4 -films. The maximum conductivity we have observed for this complex is 50 Scm −1 which corresponds to a maximum dopant concentration of approximately 26 mol-%. Thermoelectric power (TEP) measurements of lightly and heavily doped PT-FeCl 4 show that the positive TEP decreases drastically from 614 μV/K to 10.5 μV/K when the conductivity increases from 1.1 10 −5 to 10.1 Scm −1 . In heavily doped samples TEP is slightly overlinear, a phenomenon which is explained by a model based on conducting strands separated by thin potential barriers. PT-FeCl 4 -films exhibit promising stability properties, the conductivity remaining in the metallic regime for at least 16 months under ambient conditions.

Processible polyaniline complexes due to molecular recognition: Supramolecular structures based on hydrogen bonding and phenyl stacking

Abstract We show that sulphonic acid doped polyaniline (PANI) can be plasticized using certain low-acidic organic compounds consisting of ring structures and hydrogen bonding moieties that are able to “recognize” the complementary moieties of the doped PANI. The achieved synergistic combination of interactions consists of phenyl stacking, hydrogen bonding and charge transfer due to protonation. Fusible electrically conducting supramolecular structures are rendered, as suggested also by quantum chemical calculations. For example, PANI doped by methanesulphonic acid, toluenesulpnonic acid, dodecylbenzenesulphonic acid, or camphorsulphonic acid can be plasticized by dihydroxybenzenes and bisphenols to obtain fusible particle-free films at the resolution of optical microscope. The generalization to other plasticizers and other aromatic polymers, such as polypyrrole, is obvious.

Critical aspects of organic polymer batteries

Abstract For many years a serious challenger to the present day lead-acid and Ni/Cd-batteries has been sought. After the invention of electronically conducting polymers, these have belonged to the potential electrode materials for tomorrows batteries. However, in many respects conducting polymers show a limited performance, and have thus still a long way to go until commercialization in batteries. In this presentation we discuss, in practical terms, many of the key parameters of organic polymer batteries. It is shown that low density and low charge density per surface area cause serious problems where energy density and electrode areas are concerned. One can, with a skilful design, achieve energy densities at best comparable to that of the lead-acid battery. In specific energies, however, a better performance can be forecasted.

TEM and WAXS characterization of polyaniline/PP fibers

Abstract PANIPOL ™ / polypropylene (PP) blends can be melt spun into conducting fibers, with a diameter of ca. 20μm. They have been characterized by TEM and WAXS. We find that the fibers have a highly ordered polyaniline (PANI) structure and exhibit a phase separated morphology with continuous fibrils of PANI in the PP-matrix. The PANI phase has a well developed three dimensional order with a layer structure parallel to the PANT chains and the fiber axis. The layer distance is ~2.9 nm as observed from the micrographs and from the low angle X-ray reflection. The presence of higher order X-ray reflections and the narrow peak width indicate long range order of ~13 nm. The continuous PANT phase gives rise to an electrical conductivity of up to 10 −3 S/cm.

Thermoreversible gels of acid doped polyaniline : Electrical switching based on network transitions

Abstract Thermoreversible gelation of polyaniline (PANI) dissolved in dodecyl benzene sulphonic acid (DBSA) is here demonstrated for systems containing ca. 7–16 wt % of PANI. Below the gel melting temperature such materials show elastic behavior, i.e. recovery of dimensions after stress release, and frequency independent dynamic moduli. Above the gel melting temperature, the materials are viscous fluids showing frequency dependent dynamic moduli. The gel melting temperature depends on the weight fraction of PANI dissolved in DBSA, It is shown that thermoreversible gelation allows temperature controlled reversible switching of electrical conductivity.

Conductivity tailoring of blends of fusible polyaniline and polyolefins by viscosity ratio

Several types of plasticizers allow acid doped polyaniline (PANI) to become fusible, if their specific interaction to acid doped PANI is sufficiently strong. We show that if the counter-ion and the plasticizer are additionally amphiphilic, a surface active comb-shaped macrosalt is rendered, whose phase continuity in blends of nonpolar polymers can be tailored by their viscosity ratio, as in conventional polymer blends.