T. Taka

Thin polyaniline films in EMI shielding

Abstract Electromagnetic interference shielding efficiency has been measured for highly electrically conducting Polyaniline-Camphor Sulfonic Acid. The polymer is spin coated from m-cresol solution on an electrically insulating substrate as a 1–30 μm thick layer having a conductivity of 10–100 S/cm. The shielding efficiencies (SE) for these electrically thin polyaniline films have been measured in the near-field with a dual-chamber box and in the far-field with a transmission line method in the frequency range 0.1–1000 MHz. The measurements show that SE depends primarily on the surface resistance both in the far-field and the near-field. An additional effect >10 dB is seen when the two layer structure is measured in the near field. By using layer structures, the SE is >40 dB up to ca. 100 MHz in the near-field and 39 dB at 1 GHz in the far-field.

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.

EMI shielding measurements on poly(3-octyl thiophene) blends

Abstract The use of conducting polymers for EMI shielding is a potential application. Measurements have been made on poly(3-octyl thiophene) (P3OT) blends with polystyrene (PS), polyvinyl chloride (PVC) and ethyl-vinyl acetate (EVA) as matrix materials.

Doping and dedoping processes in poly (3-alkylthiophenes)

Abstract Doping, thermal dedoping and degradation processes in poly(3-octylthiophene) and poly(3-decylthiophene) have been studied. The doped state is unstable. The dedoping decay rate of conductivity depends on the dopant, dedoping degree (or conductivity) and temperature. The temperature dependence follows the Arrhenius law. The most stable dopant studied was FeCl3. Other dopants, I2, PF6− and organic acid anions had orders of magnitude higher conductivity decay rates. Dedoping is associated with degradation of the polymer, especially when doped with FeCl3.

Humidity dependency of electrical conductivity of doped polyaniline

Abstract The electrical conductivity of polyaniline doped with hydrochloric and sulphonic acid was studied as a function of relative humidity and time. The conductivity was measured at five different humidity levels from dry air to 98 % relative humidity at room temperature. A dry environment leads to a decrease in the conductivity, whereas the conductivity increases as the humidity is increased. The changes in the conductivity have a high degree of reversibility which indicates that no degrading chemical reactions occur.

Conductivity and structure of DBSA-protonated polyaniline

Abstract The discovery of a processable and conducting polyaniline complexes including functionalized sulphonic acids is an important discovery in the field of conjugated polymers. The conductivity, electronic and crystalline structure properties of polyaniline protonated with dodecylbenzenesulphonic acid are proportional to the molar concentration of the acid. The protonation leads to a layer structure evident in X-ray diffraction patterns and the crystallinity follows a growth as a function of the acid concentration similar to the conductivity increase. The electronic structure measured by UV-VIS spectroscopy shows an increase in the polaron concentration up to an acid concentration of 0.35 after which a broadening of the peak indicates the formation of a polaron band.

Layered structure with side chain crystallinity in undoped poly(3-alkyl thiophenes)

Abstract The order formation of alkyl-substituted rigid polymers, like poly(3-alkyl thiophenes), is dependent on the length of the alkyl side chain. The formation of a layered structure can be observed by X-ray diffraction experiments. A linear relationship with the d-spacing for (200) plane and n has been obtained along with the observation of the endotherms for the mesophase transition by the thermal analysis. The endothermic transition temperatures observed by DSC decrease with the increasing number of carbons (n) in the alkyl side chain. Side chain crystallization becomes possible when n is larger than 10, resulting in hexagonal packing of the alkyl chains between the main chain layers.

Determination of impurity effects of solubility and processability of poly(3-octyl thiophene)

Abstract Impurities in poly(3-octyl thiophene) negatively affect the solubility and mouldability of the polymer. To ensure good melt processability and solubility the polymer has to very pure. The structure of the polymer and the stability of the undoped polymer was also studied.

Degradation studies of doped and dedoped poly(3-octyl thiophene)

Abstract The conductivity of poly(3-alkylthiophenes) has been found to decrease by thermal dedoping. The doped state of the conducting polymer is unstable because the doped state has a higher energy than the dedoped or the undoped state. The conductivity decreases exponentially with time and the change can be fitted to an Arrhenius type equation. The change of conductivity is accompanied by a degeneration of the polymer.

Humidity dependency of electrical conductivity in poly(3-octylthiophene)

Abstract The electrical conductivity of thick samples of poly(3-octylthiophene) has been studied as function of relative humidity at room temperature. The conductivity increases in dry air and increasing the humidity level of the surrounding atmosphere induces a dedoping reaction resulting in decay of the electrical conductivity. Thick samples have been studied since interest was focused on possible use in bulk applications of the polymer. The effect of doping level was also studied.