Srinivasan Palaniappan

Esterification of carboxylic acids with alcohols catalyzed by polyaniline salts

Polyaniline salts such as polyaniline hydrochloride, sulfate, nitrate, phosphate and p-toluenesulfonate are used as catalysts in the esterification of carboxylic acids with alcohols. The activity, recovery, reusability and handling of the catalysts are found to be good. This process is being reported for the first time.

Emulsion polymerization pathway for preparation of organically soluble polyaniline sulfate

In this work, aniline was polymerized directly to polyaniline sulfate salt without using protic acid. Polyaniline sulfate salt was prepared by an emulsion polymerization pathway using surfactants such as anionic surfactant (sodium lauryl sulfate), cationic surfactant (cetyltrimethylammonium bromide) and non-ionic surfactant (polyethylene glycol octadecyl ether). Anionic/cationic surfactants yield polyaniline sulfate salt in organic phase and non-ionic surfactant yields polyaniline sulfate in powder form. The dopant, i.e. sulfate ion, in polyaniline sulfate salt was generated from ammonium persulfate which was used to oxidize aniline. Ammonium persulfate acts both as an oxidizing agent and as a doping agent in the polymerization process of aniline to polyaniline sulfate salt. The spectral and electrical properties of the polyaniline salt synthesized by the emulsion polymerization pathway are compared with those of the polyaniline salt prepared by an aqueous polymerization pathway using sulfuric acid as protic acid.

Polyaniline Salts and Complexes as Catalyst in Bisindole Synthesis

Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H2SO4, HNO3 and H3PO4), organic acid — p-toluene sulfonic acid (PTSA) and Iodine (I2). Polyaniline complexes are also prepared using Lewis acids (BF3, AlCl3 and SnCl2). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the first time in bisindole synthesis. Bisindole (3,3′-bis(indolyl)phenylmethane) is obtained in excellent yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.

Benzoyl peroxide oxidation route to polyaniline salt and its use as catalyst in the esterification reaction

Aniline was oxidized to polyaniline salt using benzoyl peroxide as an oxidizing agent in the presence of sulfuric acid and sodium lauryl sulfate surfactant. The polymer sample was characterized using infrared, X-ray diffraction, particle size, resistance and density measurements. Polyaniline salt was used as catalyst for the esterification reaction of carboxylic acids with methanol. The process is being reported for the first time. Preparation of catalyst, recovery and reusability of the catalyst are found to be good.

Tetrahydropyranylation of alcohols catalyzed by polyaniline salts

Polyaniline salts have been used as catalysts for the tetrahydropyranylation of alcohols in a process being reported for the first time. The catalytic use of polyaniline salts is practical because of their easy preparation, recovery and reusability.

Emulsion polymerization pathway for preparation of polyaniline-sulfate salt, using non ionic surfactant

In this work, aniline was polymerized directly to the polyaniline‐sulfate salt without using a protonic acid. The polyaniline‐sulfate salt was prepared by emulsion polymerization, using a non ionic surfactant such as poly(ethylene glycol)–block poly(propylene glycol)‐block poly(ethylene glycol). In the aniline oxidation process, to give the polyaniline salt by ammonium persulfate, the sulfate ion is generated from ammonium persulfate and doped on to the polyaniline. Ammonium persulfate acts both as an oxidizing agent, as well as the protonating agent in the aniline polymerization process, to give the polyaniline salt. This result indicates that the effect of sulfate ion, generated by ammonium persulfate during oxidation of aniline to the polyaniline salt, may be taken into consideration in the polymerization process of aniline.

PANI-HBF4: A Reusable Polymer-Based Solid Acid Catalyst for Three-Component, One-Pot Synthesis of 3-Substituted Amino Methyl Indoles Under Solvent-Free Conditions

Abstract A simple, fast, efficient, high-yielding, and green process is developed for one-pot, three-component synthesis of 3-substituted amino methyl indoles under solvent-free conditions using polyaniline salt as polymer-based reusable solid acid catalyst at room temperature. The advantages of polyaniline salt catalyst are ease of synthesis and handling, low cost, versatality, and recyclability. GRAPHICAL ABSTRACT

Improving the electrochemical performance by sulfonation of polyaniline-graphene-silica composite for high performance supercapacitor

ABSTRACT In this work, to increase the specific capacitance and energy density of reduced graphene oxide–silica composite (RGO-SiO2), pseudocapacitive behaviour of polyaniline is introduced to RGO-SiO2(PANI-RGO-SiO2) and further improved by sulfonating the polyaniline system (SPANI-RGO-SiO2). Formation of SPANI-RGO-SiO2 is confirmed from IR and XRD analyses. SPANI-RGO-SiO2 shows nanorods morphology with less crystalline nature. The specific capacitance of RGO-SiO2 is increases from 24 to 780 F g−1 with sulfonation of polyaniline in RGO-SiO2. Retention in the specific capacitance value of SPANI-RGO-SiO2 is 85% with that of its original value of 780 F g−1 with coulombic efficiency (96–99%). GRAPHICAL ABSTRACT

Simultaneous Oxidation and Doping of Aniline to Polyaniline by Oxidative Template: Electrochemical Performance in Supercapacitor

Polyaniline salts containing sulfuric acid and cetyltrimethylammonium sulfate dopants were prepared by aqueous (PANI-Aq), emulsion (PANI-Em), and interfacial (PANI-In) polymerization pathways using cetyltrimethylammonium peroxodisulfate as an oxidative template. Formation of polyaniline was confirmed from infrared and X-ray diffraction spectral results. Value of conductivity (15 S cm−1) of the polyaniline salt prepared by emulsion polymerization pathway was higher with that of the conventional polyaniline salt. PANI-Aq, PANI-Em, and PANI-In showed layered, flower petals, and nanorod and flower petals morphologies, respectively. These polyaniline salts were used as electrode in supercapacitor. Specific capacitance of PANI-Em, PANI-Aq, and PANI-In were 520, 484, and 474 F g−1, which were higher than the conventional PANI-H2SO4 salt (390). Energy density was 26, 24.2, and 23.6 Wh kg−1, respectively at a power density of 120 W kg−1. After 3000 charge-discharge cycles, retention in the specific capacitance values of polyaniline salts was 86% (PANI-Em), 85.4% (PANI-Aq) and 76.1% (PANI-In). GRAPHICAL ABSTRACT

Benzoyl peroxide oxidation route to polyaniline salt and its use as catalyst in tetrahydropyranylation of decanol

In this work, benzoyl peroxide is used as an oxidizing agent to oxidize aniline to polyaniline salt in the presence of protic acids such as sulfuric or nitric acid. The polymer samples are characterized by infrared, X-ray diffraction, particle size, resistance and density measurements. Polyaniline salts are used as catalysts for the tetrahydropyranylation of decanol. This process is being reported for the first time. The catalytic use of polyaniline salt is quite practical because of its easy preparation, recovery, and reusability of the catalyst.