E.J. Oh

Electromagnetic interference shielding efficiency of polyaniline mixtures and multilayer films

Abstract Electromagnetic interference shielding efficiency (SE) of the mixtures of polyaniline (PAN) and conducting powders such as silver (Ag), graphite, and carbon black is measured in the frequency range from 10 MHz to 1 GHz by using ASTM D4935-89 technique. The measured SEs of the mixtures are from 20 dB to 50 dB, which agree with theoretical values obtained from a good-conductor approximation. The SEs of the system increase with increasing DC conductivity. For the mixture of emeraldine base form of PAN and Ag powder doped with hydrochloric acid, the SE iElectromagnetic interference shielding efficiency (SE) of the mixtures of polyaniline (PAN) and conducting powders such as silver (Ag), graphite, and carbon black is measured in the frequency range from 10 MHz to 1 GHz by using ASTM D4935-89 technique. The measured SEs of the mixtures are from 20 dB to 50 dB, which agree with theoretical values obtained from a good-conductor approximation. The SEs of the system increase with increasing DC conductivity. For the mixture of emeraldine base form of PAN and Ag powder doped with hydrochloric acid, the SE iElectromagnetic interference shielding efficiency (SE) of the mixtures of polyaniline (PAN) and conducting powders such as silver (Ag), graphite, and carbon black is measured in the frequency range from 10 MHz to 1 GHz by using ASTM D4935-89 technique. The measured SEs of the mixtures are from 20 dB to 50 dB, which agree with theoretical values obtained from a good-conductor approximation. The SEs of the system increase with increasing DC conductivity. For the mixture of emeraldine base form of PAN and Ag powder doped with hydrochloric acid, the SE iElectromagnetic interference shielding efficiency (SE) of the mixtures of polyaniline (PAN) and conducting powders such as silver (Ag), graphite, and carbon black is measured in the frequency range from 10 MHz to 1 GHz by using ASTM D4935-89 technique. The measured SEs of the mixtures are from 20 dB to 50 dB, which agree with theoretical values obtained from a good-conductor approximation. The SEs of the system increase with increasing DC conductivity. For the mixture of emeraldine base form of PAN and Ag powder doped with hydrochloric acid, the SE is46 dB with70 μm thickness. Chemical doping in PAN mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed. The effects of multilayer of PAN on the SE are presented.6 dB with70 μm thickness. Chemical doping in PAN mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed. The effects of multilayer of PAN on the SE are presented.6 dB with70 μm thickness. Chemical doping in PAN mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed. The effects of multilayer of PAN on the SE are presented.6 dB with70 μm thickness. Chemical doping in PAN mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed. The effects of multilayer of PAN on the SE are presented.

Electrical, magnetic, and structural properties of chemically and electrochemically synthesized polypyrroles

Abstract We report the results of temperature-dependent dc conductivity (σdc(T)), EPR (electron paramagnetic resonance) magnetic susceptibility, and XPS (X-ray photoelectron spectroscopy) experiments for chemically and electrochemically synthesized polypyrrole (PPy) samples. For chemically synthesized dodecylbenzenesulfonic acid (DBSA) or naphthalenesulfonic acid (NSA) doped PPy samples (PPy-DBSA or PPy-NSA, respectively) soluble in m-cresol solvent, dc conductivity and its temperature dependence show the strong localization behavior, while those of electrochemically synthesized PPy doped with hexafluorophosphate (PPy-PF6) are in the critical regime. Pauli susceptibility (χp) and the density of states are obtained from the temperature dependence of EPR magnetic susceptibility. The density of states of chemically synthesized PPy is one-third of that of electrochemically synthesized PPy. From the analysis of the area ratio of carbon 1s XPS peak, the disorder effect due to interchain links or side chains of PPy-DBSA (m-cresol) samples is ∼22%, while that of PPy-PF6 samples is ∼33%. This result indicates that the percent of interchain links or side chains of chemically synthesized PPy-DBSA (m-cresol) samples is reduced by ∼10% compared to that of electrochemically synthesized PPy-PF6 samples. We analyze that the side chains or interchain links of chemically synthesized PPy samples are relatively reduced due to the synthesis method using large size dopants, and subsequently the interchain interaction weakens. The results of EPR experiments of PPy-DBSA (m-cresol) samples with different doping levels are discussed.

Charge transport studies of doped polyanilines with various dopants and their mixtures

Abstract We report the results of temperature (T) dependence of dc conductivity (σdc) for polyaniline (PAN) pellet samples with various dopants (BSA, NSA, ISA, and CSA) in organic solvents (m-cresol, CHCl3, BeOH) and the mixtures of PAN-DBSA (CHCl3) and PANBSA (m-cresol). σdc(T) of PAN pellets varies with dopants in the same solvent. However using different solvent, σdc(T) with the same dopant dramatically changes, which indicates that transport properties, can be controlled by both dopants and solvents. The mixture of PAN-DBSA (CHCl3) and PAN-BSA (m-cresol) induces the increase of σdc and the variation from the insulating regime to the critical one.

Investigation of corrosion protection of iron by polyaniline blend coatings

The polyaniline(PANI) blends were made by adding polyaniline protonated with camphorsulfonic acid(PANI-CSA), dodecylbenzene sulfonic acid(PANI-DBSA) in polymethylmetacylate(PMMA) and epoxy, respectively. Poly-o-ethoxyaniline(PEtOAN) doped with HCl(PEtOAN-Cl), HNO 3 (PEtOAN-NO 3 ), and HBF 4 (PEtOAN-BF 4 ) in water soluble epoxy(WSE) was also prepared for protective coating on iron surface. The protective properties of the PANI/PMMA, PANI/epoxy and PEtOAN/WSE blend coatings on pure iron have been studied in 3 wt.% NaCI solution by potentiodynamic polarization measurements and open circuit potential measurements. It has been found that the coatings containing PANI and PEtOAN showed better corrosion protection in 3 wt.% NaCI solution than the single component coatings such as epoxy, PMMA or WSE.

Synthesis and characterization of alcohol soluble polypyrrole

Soluble polypyrrole (Ppy-DEHS) in various alcohols are chemically synthesized using functional doping agent, di(2-ethylhexyl) sulfosuccinate sodium salt (NaDEHS), which has non-polar alkyl chains and polar oxygen atoms. The weight average molecular weight (Mw) of Ppy-DEHS appeared to be 32,547 which corresponds to 158 pyrrole rings in the polymer chain. Ppy-DEHS films cast from the various alcohols showed the electrical conductivities of 10 -2 ∼ 10 -5 S/cm at room temperature. This improved solubility in alcohol was explained in terms of the hydrogen bonding between alcohol and oxygen in sulfosuccinate.

UV-Vis./NIR and transport studies of chemically synthesized soluble polypyrrole

Abstract Doped polypyrrole which is soluble in various organic solvents ( m -cresol, chloroform, DMSO, NMP etc.) is synthesized. Homogeneous solutions prepared from the solvents show different behaviors at near IR region depending on the solvent used. The results may be explained by PPy conformation change depending on polarity and aromatic interaction of solvents and dopants. Amorphous X-ray diffraction pattern is observed in flexible free standing films cast from these solutions. The electrical conductivity of the materials is 10 −2 ~ 10 0 S/cm at room temperature. Temperature dependence of dc conductivity ( σ dc ) indicates that these materials show the three dimensional variable range hopping (VRH) model and show the relatively strong localization of charge. From the EPR experiment of PPy-NSA ( m -cresol) sample, the density of state of the system is estimated as ~0.06 states/eV ring.

Preparation of polyaniline free standing film by controlled processing and its transport property

Abstract Polyaniline(emeraldine base : EB) free standing films with different degree of cross-linking prepared from NMP solution were stretch-oriented at 110 ∼ 180°C up to 1 1 0 = 4 then doped with 1N HCl. Free standing films of polyaniline doped with various functionalized acid such as camphorsulfonic acid (HCSA), dodecylbenzenesulfonic acid (HDBSA), methane sulfonic acid(HMSA) etc. were prepared in various solvents such as o -chlorophenol, chloroform, etc. Processing conditions were determined by measuring UV/Vis spectra of solution. Films prepared from these solutions showed the conductivities of 10 −1 ∼ 220S/cm. To investigate the effect of molecular weight on the properties of polyaniline films, high molecular weight polyaniline (Mw ∼ 309,000) was synthesized at ∼ −30°C. It was found that mechanical property, crystallinity, conductivity of the films depend on the drying process and type of solvent. Transport properties for various polyaniline free standing fims will be discussed from the results of DC, microwave conductivity and thermopower measurements.

Electrochemical redox properties of chemically synthesized soluble polypyrrole

Abstract The soluble polypyrrole(PPy) was synthesized and its electrochemical properties were investigated. The polymer was synthesized by oxidative coupling of monomers in aq. (NH4S2O8/dodecylbenzene sulfonic acid(DBSA) at 0°C. The polymer was soluble in various organic solvents. The absorption spectrum change of the DBSA-PPy solution depends on the solvent used. Free standing films cast from these solutions showed amorphous X-ray diffraction pattern and electrical conductivity of 0.1~6.0 S/cm at room temperature. Thin PPy films on ITO electrodes showed cyclic voltammograms(CV) which have similar shape to those of the electrochemically prepared one. The electrochemical redox properties of these films may be based on the direct reaction of PPyPPy2+.

Charge transport study of chemically synthesized polypyrroles soluble in organic solvents

Abstract We report the results of temperature (7) dependence of dc conductivity (σdc), microwave dielectric constant, and EPR experiment for soluble polypyrrole (PPY) samples with different dopants (DBSA and NSA) prepared using various organic solvents (NMP, m-cresol, CHCl3, and DMSO). The three dimensional variable range hopping (VRH) model provides the best fit to the data, while the slope of σdc(T) varies with dopants and solvents used. σdc at room temperature is ~ 0.2 0.01 S/cm and the localization length is estimated as 5 A, which indicates the relatively strong localization of charge for these materials. We discuss the relation between the polarity of solvent and σdc(T). From EPR experiment, the density of states of the systems is estimated.

Preparation and properties of fullerene doped polyaniline

Abstract C 60 (0.5≈15mol%) doped polyaniline(emeraldine base:EB) was prepared from NMP(N-methyl-2-pyrrolidinone)/toluene solution. Free standing films cast from this solution showed the conductivities up to 6.2×10 −5 S/cm. UV/Vis, spectra of C 60 doped EB solution in NMP/toluene showed the decrease in absorption intensity as the content of C 60 increased. The first and the second redox processes in the cyclic voltammogram were observed to shift to higher potential. It is believed that the former is attributed to the steric effect which is due to bulky C 60 and the latter is attributed to the electronic effect which is due to the electron withdrawing nature of C 60 . From the above results, the formation of charge transfer complex between the polymer as electron donor and C 60 as electron acceptor was suggested. Also thermal stability of C 60 doped polyaniline was compared to that of parent polyaniline.