S. Venkatachalam

Oligomeric phthalocyanine modified polyaniline — an electrode material for use in aqueous secondary batteries

Abstract Polyaniline (PANI) and oligomeric phthalocyanine (PPC) are prepared and characterized by spectroscopic and analytical methods. They are blended in different proportions and their blends are characterized by cyclic voltammetry, electrochemical impedance measurements and are studied as electrodes in aqueous secondary batteries. The cell Zn/0.1 M ZnSO 4 /PANI—PPC is constructed and its charging—discharging behaviour is studied at different current densities. The effect of oligomeric phthalocyanine content on the cycle stability and the cell performance was also studied. The impedance spectra of the system were studied in two-electrode and three-electrode modes. The charge transfer resistance is found to be potential dependent. The complex impedance of the system is found to be independent of frequency at high frequencies and it shows a complex capacitive behaviour at low frequencies. The cell shows a maximum capacity of 93.3 Ah kg −1 for a particular ratio of PANI to PPC in the system. The current efficiency was close to 100% over at least 1000 complete cycles when cycled between 1.2 to 0.6 V at a constant current of 0.9 mA cm −2 . The cell performance is stable at current densities ranging from 0.9 to 10 mA cm −2 .

Permanganate ion supported over crosslinked polyvinylamine as an oxidising agent for alcohols

Abstract Crosslinked polyacrylamide was prepared by the free radical polymerization of acrylamide and divinyl benzene and it was converted to crosslinked polyvinylamine by Hofmann’s degradation reaction using hypobromite. The polyvinylamine so obtained was functionalized with permanganate group to get the polyvinyl ammonium permanganate resin. The catalyst was evaluated to study the oxidation of six alcohols to their corresponding carbonyl compounds in cyclohexane medium. The extent of oxidation reaction with respect to reaction time and the nature of alcohol was studied. The effect of crosslinking the backbone polymer on the reaction was also studied and 5% crosslinking was found to be optimum. The spent polymeric reagent could be regenerated in single step many times with out loss of its capacity. The catalytic resin was insoluble in the medium during oxidation and, therefore, filtration and purification of the products were easy.

Structural characterization of hydroxyl terminated polyepichlorohydrin obtained using boron trifluoride etherate and stannic chloride as initiators

Abstract Epichlorohydrin was polymerized using boron trifluoride etherate or stannic chloride as initiators in presence of diols. The molecular weight of the polymer increased with increase in the ratio of epichlorohydrin to the diol in the reaction mixture. The polymers were characterized by IR, proton NMR and 13 C NMR analysis. The terminal hydroxyl groups of the polymers were characterized by derivatizing them using trifluoro acetic anhydride and analyzing the resulting ester by NMR. Both primary and secondary hydroxyls were present in the polymer. The primary hydroxyl terminals of the polyepichlorohydrin (PECH) prepared using stannic chloride initiator were twice the amount of that present in the polymer prepared using BF 3 etherate initiator. The 13 C NMR spectrum of PECH prepared using BF 3 etherate indicates that the polymer backbone is rich in H–T diad. Both cationic and co-ordination mechanisms operate during the polymerization in the presence of SnCl 4 and the 13 C NMR spectrum of the polymer showed more of T–T and H–H sequences.

Electrically-conductive nickelphthalocyanine polymer

Thermal treatment of nickelphthalocyanine polymer having terminal carboxyl groups results in the formation of highly-conjugated structures and mobile radical defects, which cause an increase in the room-temperature electrical conductivity by seven orders of magnitude. The polymer was characterized by i.r., ESCA and elemental analyses. The heated polymer shows large paramagnetic susceptibilities and a dramatic increase in e.s.r. linewidth. The linewidth, intensity of e.s.r. and the magnetic susceptibility of the heated polymer decrease with increasing temperature. These results are explained by the presence of both localized and delocalized spins in the polymer network. The presence of adsorbed oxygen influences the ratio of the two types of spins. At low temperatures, localized spins dominate and at high temperatures most of the spins remain delocalized. The large electrical conductivity has been explained by the hopping of the mobile spins through the conjugated network polymer.

Rheokinetic studies on the formation of urethane networks based on hydroxyl terminated polybutadiene

Abstract Rheokinetic studies on the formation of copolyurethane networks based on hydroxyl terminated polybutadiene, poly(12-hydroxy stearic acid-co-TMP) ester polyol and different isocyanates, such as toluene-di-isocyanate, hexamethylene-di-isocyanate, isophorone-di-isocyanate and methylene-di-cyclohexyl di-isocyanate were undertaken by following the build up of viscosity of the reaction mixture during the bulk polymerization reaction between the hydroxyl telechelic pre-polymers and the di-isocyanate compounds. Linear rheokinetic plots were obtained by plotting ln(viscosity) versus time and the slopes of which, are the rate constants for the viscosity build up. The rate constants range from 0.038×10 −2 to 27.1×10 −2 min −1 and were found to have strong dependence on the isocyanate type, NCO/OH equivalent ratio ( r -value) and copolyurethane composition as well as the structural characteristics, such as functionality distribution of the pre-polymers and the nature of the hydroxyl group.

Redox active thin films of polymeric metal-free octacyanophthalocyanine

Abstract Octacyanophthalocyanine is found to undergo oxidative polymerization under electrochemical conditions at 1.6 V. The polymer was characterized by infrared and UV-Vis spectra. The polymer-coated electrode undergoes a reversible electrochemical process when cycled in various electrolytes. The coated film acts as an ion exchange membrane specific to cations. This was proved by electrochemically trapping Fe(Phen) 3 2+ ions and monitoring the cyclic voltammetric response of the incorporated cations.

Electroactive polymeric thin film based on polypyrrole incorporating metallophthalocyanine polymer

Abstract Thin films of polypyrrole doped with polymeric nickel phthalocyanine were grown on a platinum substrate by the electrochemical oxidation of pyrrole from aqueous solution containing 0.01 M pyrrole and 0.1 M sodium salt of polymeric nickel phthalocyanine as the only supporting electrolyte. The film thus prepared was characterized by i.r., u.v.-vis., e.s.c.a. and by conductivity measurements. The electrochemical behaviour of the electrode was studied by cyclic voltammetry in aqueous and non-aqueous electrolytes. The film exhibits stable conductivity and reversible electrochemical behaviour in the range of the potential investigated.

Oligomeric metallo phthalocyanine-incorporated conducting polymers

Pyrrole and aniline were polymerized electrochemically in aqueous media using sodium salt of metallo phthalocyanine oligomer possessing carboxyl terminals as the supporting electrolyte. The polymers get coated as thin films in platinum cathode, and they were characterised by IR, UV-Vis, ESCA, and electrochemical and electrical conductivity measurements. The voltammetric measurements of the oligomeric metallo phthalocyanine-incorporated polypyrrole indicate stable and reversible electrochemical behaviour in aqueous KCl media. Monomeric metallo phthalocyanine-incorporated polypyrrole was also prepared and the electrochemical properties were studied. Oligomeric nickel phthlocyanine-incorporated polyaniline shows poor electrochemical behaviour in aqueous KCl.

Electrically conducting three-dimensional (octacyano phthalocyaninato polysiloxane) polymer

Abstract Polymeric (octacyano phthalocyaninato polysiloxane) has been prepared by reacting 1, 2, 4, 5 tetracyano benzene (TCNB) with silicon tetrachloride in refluxing quinolene and hydrolysing the resulting product with dilute alkali. The product has been characterized by infrared (i.r.), ultraviolet-visible (u.v.-vis.) spectra, elemental analysis and electron spectroscopy chemical analysis (ESCA). The polymer shows improvement in electrical conductivity by six to seven orders of magnitude (10 −1 S cm −1 ) on thermal treatment.

Effect of supporting electrolytes and cathode materials on the electro-copolymerization of acrylonitrile with methacrylic acid

Abstract Copolymers of acrylonitrile with methacrylic acid were synthesized electrochemically. The reaction system consisted of dimethyl formamide as solvent and various quarternary ammonium salts as supporting electrolytes. The influences of supporting electrolytes and electrode materials on the compositions of the copolymers were investigated. The copolymers were characterized by i.r., NMR and elemental analyses. Thermal decomposition studies of the polymer in air are also discussed.