Dinesh Chandra Trivedi

Shielding of electromagnetic interference using polyaniline

Since the discovery in 1977 of the metallic properties of molecularly doped polyacetylene, there has been rapid growth in the field of electronically conducting polymers [1-5]. The interest in this area is mainly due to the numerous technological applications of conducting polymers as active electrode materials in energy storage [6], opto-electronic devices [7], display devices [8, 9 ] and their envisaged application for the control of electromagnetic radiation (EMR) and dissipation of electrostatic charge [10-12]. Polyaniline (PAn) is particularly interesting because of the presence of the chemically flexible N H group in the polymer backbone which not only takes part in the protonation/deprotonation but also contributes to 7r-band formation [13], thus ensuring greater environmental stability. PAn can be obtained either by chemical or electrochemical method and does not involve any special precautions [14-16[. Although it is easily synthesized in bulk, its use is restricted due to its unprocessibility by normal melt or solution techniques. For many applications, such as in the control of electromagnetic interference (EMI), dissipation of electrostatic charge (ESD) requires a thin conducting coating on a flexible surface. Polyaniline, unlike metallic coating, is free from corrosion and is very suitable under a highly corrosive atmosphere where other conducting coatings fail. Due to the reactivity of synthetic fabrics like Nylon, Terylene and glass fabric towards mineral acids, we have used organic acids like benzenesulfonic acid (BSA), para-toluenesulfonic acid (PTSA), 5-sulfosalicylic acid (SSA) and 4-hydroxybenzenesulfonic acid as media for grafting PAn. The detailed study using these acids on the properties of polyaniline has been reported elsewhere [8, 9, 17]. The effect of these acids on charge transport, optical and magnetic properties which are quite different to those of mineral acids (like persistence

Investigations on the effect of 5-sulfosalicylic acid on the properties of polyaniline

Abstract Results of the investigation of the chemical and electrochemical polymerization of aniline in 5-sulfosalicylic acid medium and its characterization by electrochemical and spectroscopic techniques are presented. The investigation reveals that 5-sulfosalicylic acid as a dopant not only enhances electrochemical stability of polyaniline at higher potentials but also yields a polymer which is soluble to the extent of 11 g/l in DMSO. The characterization of conducting polyaniline thus obtained was carried out by electronic and vibrational spectra, 1 H NMR in DMSO-d 6 , X-ray powder diffraction, thermal analysis and by electrochemical techniques.

Polyaniline as an electrode material for magnesium reserve battery

Abstract The results of the investigation on the use of polyaniline (PANI) as a cathode material in a battery configuration, having magnesium as anode and a neutral aqueous solution of one of the magnesium salts such as perchlorate, chloride and bromide as an electrolyte, are presented. This system shows a open circuit voltage in the range 1.6–1.8 V. The study indicates that the capacity of the system largely depends upon the anion present in the electrolyte.

Grafting of electronically conducting polyaniline on insulating surfaces

A method is described to graft conducting polyaniline onto glass fabric, glass wool and nylon cloth to impart flexibility and mechanical strength to the polyaniline, which is otherwise powdery and untracable. These flexible conductive surfaces can find application as antistatic shields.

A low-cost lead-acid battery with high specific-energy

Lightweight grids for lead-acid battery grids have been prepared from acrylonitrile butadiene styrene (ABS) copolymer followed by coating with lead. Subsequently, the grids have been electrochemically coated with a conductive and corrosion-resistant layer of polyaniline. These grids are about 75% lighter than those employed in conventional lead-acid batteries. Commercial-grade 6V/3.5Ah (C20-rate) lead-acid batteries have been assembled and characterized employing positive and negative plates constituting these grids. The specific energy of such a lead-acid battery is about 50 Wh/kg. The batteries can withstand fast charge-discharge duty cycles.

Conducting Fabric-reinforced Polyaniline Film Using p-Chlorophenol as Secondary Dopant for the Control of Electromagnetic Radiations:

Polyaniline (PAn) is a commercially viable conducting polymer exhibiting enough metallic conductivity to replace carbon/metal filled composites as a shield to control electromagnetic radiations. In this paper, we discuss the process to achieve a pore-free conducting fabric reinforced with PAn. The process involves the pretreatment of glass fabric before the in situ polymerization of aniline in the presence of either p-toluenesulfonic acid (PTSA) or camphor-10-sulfonic acid (CSA). The conducting E-glass fabric is coated with a conductive paste prepared from PAn-PTSA or PAn-CSA/p-chlorophenol (PCP) as the secondary dopant come solvent at 60 C to achieve a pore-free flexible conducting surface. The reinforced conducting fabrics are characterized by UV-Vis spectroscopy, conductivity, scanning electron microscopy (SEM), X-ray diffraction study (XRD), and thermogravimetric analysis (TGA). The electromagnetic interference shielding effectiveness (EMI SE) studies are carried out using the co-axial transmission line method in the frequency range of 0.1-1000 MHz. The pore-free conducting fabric reinforced with PAn-PTSA/PCP and PAn-CSA/PCP of 3 mm thickness offered an EMI SE of 58 and 55 dB at 1000 MHz. The study indicates that the SE increases with the increase in thickness and conductivity of the test coupon.

Electron localization length in polyaniline

Electrical DC conductivity, magnetic susceptibility, and EPR measurements are used to investigate the electron localization behavior of polyaniline as a function of the dopant type using seven sulfonic acid based doping acids. In spite of differences in the magnitude and the temperature dependences of DC conductivity and magnetic susceptibility data, the experiments reveal a localization length of approximately 30 A for all the samples. We conclude that this result is essentially due to disorder in the basic morphological structure of a polymer that seems to be determined, among other factors, by the nature of the monomeric units comprising the polymer chains.

High Specific-Energy Lead-Acid Batteries Through Organic Metals

A novel room-temperature route to corrosion protect lead-coated plastic grids with an organic metal, namely, polyaniline, for producing commercial-grade high specific-energy 12 V/45 Ah lead-acid batteries is reported. The specific energy of these lead-acid batteries is found to be ca. 45 Wh/kg as against about 30 Wh/kg for conventional lead-acid batteries. It is believed that the study reported here will open up a new realm of possibilities for lead-acid battery development, and will contribute directly towards lowering the cost of both battery materials and manufacturing.

Composites of Polyaniline for Antistatic Applications

The preparation of composites of conducting polymers has become a new area of research because of their technological importance. This paper describes the preparation of conductive polyaniline [PAn] composites, whose resistivity lies between 60 Ω to 1000 Ω /□. The study indicates that these composites may prove useful materials for dissipation of electrostatic charge (ESD).