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Dive into the research topics where J.-E. Österholm is active.

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Featured researches published by J.-E. Österholm.


Synthetic Metals | 1988

Thermochromic and solvatochromic effects in poly(3-hexylthiophene)

Olle Inganäs; William R. Salaneck; J.-E. Österholm; Jukka Laakso

Abstract We report thermochromic and solvatochromic effects in the soluble conductive polymer poly(3-hexylthiophene). Thin solid films of the polymer change colour at higher temperatures. The colour of solutions of the polymer can be changed by varying the composition of the solvent. Optical absorption in good solvents is similar to that of thin solid films at higher temperatures, while in poor solvents, absorption features similar to those found in solid films at low temperatures are observed. We discuss these effects with reference to the existence of a hitherto disregarded type of conformational defect, conformons. These are rotational defects on the polymer chain, leading to loss of planarity. High vacuum studies of the thermochromic effect in thin films using X-ray photoemission spectroscopy support this interpretation. The standard series of defects in conductive polymers, solitons, polarons and bipolarons, may have to be extended to include conformons.


international conference on software maintenance | 1994

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

Olli Ikkala; Jukka Laakso; K. Vakiparta; Esa Virtanen; Heikki Ruohonen; Hannele Järvinen; T. Taka; P. Passiniemi; J.-E. Österholm

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.


Synthetic Metals | 1989

Melt and solution processable poly(3-alkylthiophenes) and their blends

J.-E. Österholm; Jukka Laakso; Per Nyholm; H. Isotalo; H. Stubb; Olle Inganäs; William R. Salaneck

Abstract We report on the properties of melt and solution processable poly(3-alkylthiophenes), P3AT, and on the fabrication of electrically conducting polymer blends consisting of P3AT, specifically poly(3-octylthiophene), POT, and a thermoplastic matrix polymer made using ordinary melt processing techniques. The POT used in this work was synthesized using two different chemical polymerization techniques. Films made from as-synthesized POT powder, either by solution casting or melt processing techniques were found to be easily doped by electron acceptors to conductivities of 20–30 S/cm. Blending of POT with thermoplastics such as ethylenevinylacetate copolymer, EVA, in the molten state yields polymer blends with excellent mechanical properties that might be doped to conductivities exceeding 1 S/cm.


Synthetic Metals | 1989

Thermochromism in thin films of poly(3-alkylthiophenes)

Olle Inganäs; Göran Gustafsson; William R. Salaneck; J.-E. Österholm; Jukka Laakso

Abstract We report spectroscopic studies fo the thermochromic effect in poly(3-alkylthiophenes). Thin solid films of poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-octylthiophene) and poly(3-decylthiophene) undergo a reversible color transition when going from low to high temperature. The optical absorption shifts to higher photon energies with higher temperature. The transition, which occurs over a broad temperature range, occurs at lower temperatures for polymers of longer alkyl side chains. The colour change can be interpreted assuming a change of polymer conformation from a rigid rod geometry at low temperatures to a random coil conformation at higher temperatures. We discuss the physics of this transition.


Synthetic Metals | 1993

Emulsion polymerization of aniline

J.-E. Österholm; Yong Cao; F. Klavetter; Paul Smith

Abstract High quality polyaniline, PANI, has been made by polymerization of aniline using a direct one-step emulsion polymerization technique. The polymerization is carried out in an emulsion comprising water and a non-polar or weakly polar organic solvent in the presence of the functionalized protonic acid dodecylbenzene sulphonic acid (DBSA). We found that using the emulsion polymerization technique, conducting PANI-DBSA complexes can be produced that exhibit high molecular weight, high conductivity and high solubility in organic solvents in the electrically conducting state . We found, furthermore, that using this technique, in-situ production of PANI-DBSA fibrils can be produced that exhibit a high aspect ratio and an exceptional degree of crystalline order and orientation.


Synthetic Metals | 1997

Electrically conductive compositions based on processible polyanilines — PANEPOL TM

Esa Virtanen; Jukka Laakso; Heikki Ruohonen; K. Vakiparta; Hannele Järvinen; M. Jussila; P. Passiniemi; J.-E. Österholm

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.


Synthetic Metals | 1993

Processable conducting polyaniline

Adam Pron; J.-E. Österholm; P. Smith; A. J. Heeger; J. Laska; M. Zagórska

Abstract It has been found that diesters of phosphoric acid with branched alkyl substituents solubilize polyaniline in its protonated (conducting) state. Polyaniline protonated with bis(2-ethylhexyl)phosphate or bis(2-methylpropyl)phosphate is highly soluble in common organic solvents such as toluene, decaline, THF and chlorinated hydrocarbons. Conducting blends with poly(methylmethacrylate) or poly(acylonitrile-butadiene-styrene) (ABS) can be prepared showing high conductivity for very low electroactive component content. Protonation of polyemeraldine base with neat esters results in a heavily plastisized mixture which can be thermally processed to give free standing films with conductivities exceeding 10 S/cm. Depending on the content of the protonating agent, time and temperature of pressing films with different Young modulus, tensile strength and elongation at break can be prepared. Similarly, conducting blends with excellent mechanical properties can be prepared from diester plasticized polyaniline and plasticized polyvinyl chloride.


Synthetic Metals | 1987

Synthesis and properties of FeCl4-doped polythiophene

J.-E. Österholm; P. Passiniemi; H. Isotalo; H. Stubb

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.


Synthetic Metals | 1989

Conducting polymer blends

Jukka Laakso; J.-E. Österholm; Per Nyholm

Abstract We report the production and properties of electrically conducting polymer blends utilizing the melt-processability properties of high molecular weight poly(3-octylthiophene), POT. We have found that polymer blends produced by mixing appropriate amounts of POT with a variety of thermoplastic matrix polymers have excellent mechanical properties and that they can be doped to yield electrically conducting polymer blends with conductivities exceeding 1 S/cm.


Synthetic Metals | 1997

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

Olli Ikkala; Lars-Olof Pietilä; P. Passiniemi; T. Vikki; Heidi Österholm; Lisbeth Ahjopalo; J.-E. Österholm

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.

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H. Stubb

Åbo Akademi University

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