Kwan Sik Jang

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.

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.

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.

Electrochemical synthesis and characterization of strechable polypyrrole films

Abstract Stretchable polypyrrole (Ppy) films with mixed dopants [di(2-ethyl hexyl)sulfosuccinate with malonic acid(MA), 4-sulfophtalic acid (SPA), dodecylbenzenesulfonic acid (DBSA) etc.] were electrochemically prepared at 0 °C and room temperature and their physical properties were examined. As the temperature employed in synthesis was lowered, the resulting films became more stretchable up to the draw ratio, L/Lo = 2.5 and showed improved thermal stability and electrical conductivity (σ : 255 S/cm). On the other hand, the films prepared at room temperature were elongated up to 1.5 times (σ : 45 S/cm). These phenomena were explained in terms of the molecular weight, structural change due to the temperature and mixed dopants used.

Enhancement of Electromagnetic Interference Shielding Efficiency of Polyaniline through Mixture and Chemical Doping

Abstract Electromagnetic interference (EMI) shielding efficiency (SE) of undoped and doped polyanilines and their mixtures with silver (Ag), graphite, and carbon black powder are measured in the frequency range from 10 MHz to 1 GHz by using ASTM (D 4935–89) technique. The measured SEs of the systems are from 20 dB to 50 dB, which agrees with theoretical values obtained from a good-conductor approximation. The SE of the system increases with increasing dc conductivity. This implies that the SE can be controlled by the intrinsic properties such as conductivity and dielectric constant. For the mixture of emeraldine base (EB) form of polyaniline and Ag powder doped with hydrochloric acid (ES/Ag), the SE is ∼46 dB with 70 μm thickness, indicating the capability of commercial applications to EMI shielding. Chemical doping in polyaniline mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed.

Synthesis and characteristics of soluble polypyrroles with mixed dopants

Abstract Soluble conducting polypyrroles(Ppy) were prepared by the oxidative polymerization of pyrrole using mixed dopants. Compared to the dodecylbenzenesulfonic acid doped polypyrrole [Ppy-DBSA (σRT ∼ 10−1 S/cm)], the Ppy with mixed dopants (Ppy-mixed dopants) showed higher absorption intensity in near IR region in UV-Vis./NIR solution spectra and partly crystalline X-ray diffraction (XRD) patterns and higher conductivity of ∼20 S/cm for free standing films. The Ppy-DBSA film showed three dimensional variable range hopping (3D-VRH) conducton while Ppy-mixed dopant systems 1D-VRH conduction. These results are explained by the packing effect of planar dopant between the polymer chains.

The correlation between structure and charge transport of polypyrroles

Abstract The results of temperature dependence of dc conductivity (σdc(T)), magnetic susceptibility (χ), and X-ray photoelectron spectroscopy (XPS) are compared for electrochemically and chemically synthesized polypyrrole (PPy) samples. From the XPS experiments, interchain links or side chains for chemically synthesized PPy soluble in organic solvents are reduced by ~ 10% compared to those of electrochemically synthesized PPy because of chemical process using large size dopant. Based on temperature dependence of σdc(T), the systems are in the insulator or the critical regime. The effects of dopant on structure and charge transport of PPy systems are discussed.

Synthesis and Characterization of Soluble Polyaniline and Its Derivatives Doped with Dialkylsulfates

Abstract Soluble polyaniline and its derivatives doped with dialkylsulfate (DAS : dimethylsulfate, diethyl sulfate, dipropylsulfate etc.) were chemically synthesized. Solubilities of polyaniline doped with DAS (PANI·DAS) powders in polar solvents and polyethoxy aniline doped with DAS (PEtOANI·DAS) powders in various alcohols were observed in the range of 3–8 wt.% and 2–5 wt.%, respectively. This improved solubility in organic polar solvents was explained with the interactions between the hydrophilic sulfonate group, polar substituent and polar solvents. Compared to that of HCl doped polyaniline, PANI·DAS showed improved thermal stability upon heat treatment at 160 °C. The electrical conductivities of PANI·DAS and PEtOANI·DAS films appeared in the range of 1.2∼2.3 S/cm and 10−2∼10−4 S/cm, respectively.

Processing Effects of the Polyvinyl-Butyrol-Based Binder on the Performance of Electroluminescent Diodes

Abstract The processing effects of polyvinyl-butyrol (PVB)-based binding organics (PBBO) on the characteristics of the ZnS:Cu electroluminescent (EL) devices are discussed. The characteristics of the EL devices fabricated using the PBBO are compared with those of devices fabricated using a membrane switch composition (MSC). It is demonstrated that the performance of the PBBO be comparable with the MSC. The brightness and the output current of devices using PBBO at 100 V and 400 Hz are 55 cd/m2 and 2.2 mA, respectively. The reliability test performed under the harsh environment (333 K and 90 % RH) exhibits the life time (time at the half of the original brightness) of device longer than 140 hr.