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S. Palaniappan - One of the best experts on this subject based on the ideXlab platform.
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High-temperature oxidation of aniline to highly ordered polyaniline–Sulfate Salt with a nanofiber morphology and its use as electrode materials in symmetric supercapacitors
Journal of Applied Polymer Science, 2010Co-Authors: S. Palaniappan, Singu Bal Sydulu, Taneeru Lakshmi Prasanna, Pabba SrinivasAbstract:In this study, for the first time, aniline was oxidized by ammonium perSulfate (APS) at higher temperatures without any protic acid, and APS acted as an oxidizing agent and a protonating agent. During the oxidation of aniline by APS, sulfuric acid formation occurred, and the sulfuric acid was incorporated into polyaniline (PANI) as a dopant. PANI–Sulfate samples were characterized by IR spectroscopy, X-ray diffraction, and scanning electron microscopy techniques. In this methodology, a highly ordered PANI–Sulfate Salt (H2SO4) with a nanofiber morphology was synthesized. Interestingly, a PANI base was also obtained with a highly ordered structure with an agglomerated netlike nanofiber morphology. PANI–H2SO4 was used as an electrode material in a symmetric supercapacitor cell. Electrochemical characterization, including cyclic voltammetry (CV), charge–discharge (CD), and impedance analysis, was carried out on the supercapacitor cells. In this study, the maximum specific capacitance obtained was found to be 273 F/g at 1 mV/s. Scan rate from cyclic voltammetry and 103 F/g at 1 mA discharge current from CD measurement. Impedance measurement was carried out at 0.6 V, and it showed a specific capacitance of 73.2 F/g. The value of the specific capacitance and energy and power densities for the PANI–H2SO4 system were calculated from CD studies at a 5-mA discharge rate and were found to be 43 F/g, 9.3 W h/kg, and 500 W/kg, respectively, with 98–100% coulombic efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
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Polyaniline-Sulfate Salt as an efficient and reusable catalyst for the synthesis of 1,5-benzodiazepines and 2-phenyl benzimidazoles
Catalysis Communications, 2007Co-Authors: U. Srinivas, Ch. Srinivas, P. Narender, V. Jayathirtha Rao, S. PalaniappanAbstract:Abstract Polyaniline-Sulfate Salt was used as an efficient catalyst for the preparation of benzodiazepines and 2-phenyl benzimidazoles in excellent yields. This method is applicable for the reaction of phenylenediamine with cyclic or acyclic ketones or aromatic aldehydes. The salient features of the present methodology are cheaper process, easy synthesis of stable catalyst, versatility and in addition, the catalyst can be easily recovered after completion of the reaction and reusable without affecting its activity.
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Efficient, convenient and reusable polyaniline-Sulfate Salt catalyst for the synthesis of quinoxaline derivatives
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Chiguru Srinivas, Chebolu Naga Sesha Sai Pavan Kumar, Vaidya Jayathirtha Rao, S. PalaniappanAbstract:Biologically important quinoxaline derivatives were prepared in excellent yields using very low amount of reusable polyaniline-Sulfate Salt catalyst from various 1,2-dicarbonyls and aromatic 1,2-diamines. This methodology is also very much useful for the synthesis of new quinoxaline derivative using sterically hindered diamine.
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Emulsion Polymerization Pathway for Preparation of Polyaniline‐Sulfate Salt, using Non Ionic Surfactant
Journal of Macromolecular Science Part A, 2005Co-Authors: S. Palaniappan, Chandrasekaran Saravanan, Amalraj JohnAbstract: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.
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Polyaniline-Supported Sulfuric Acid Salt as a Powerful Catalyst for the Protection and Deprotection of Carbonyl Compounds
Synlett, 2003Co-Authors: S. Palaniappan, Chandrasekaran Saravanan, P. Narender, Vaidya Jayathirtha RaoAbstract:Structurally different carbonyl compounds were converted into their corresponding cyclic acetals using polyaniline-Sulfate Salt as catalyst in dry toluene in excellent yield. In turn, useful deacetalization in aqueous medium was demonstrated. Chemoselective protection of carbonyl compounds was also demonstrated. The advantages of the polyaniline-Sulfate Salt are ease of preparation and handling, stability, reusability and activity.
Osvaldo Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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Aqueous two-phase systems with thermo-sensitive EOPO co-polymer (UCON) and Sulfate Salts: Effect of temperature and cation
Journal of Chemical Thermodynamics, 2017Co-Authors: Xiana Rico-castro, Marlen González-amado, Alvaro Soto, Osvaldo RodriguezAbstract:Poly(ethylene glycol-ran-propylene glycol) lies within a family of thermo-separating polymers (commercialized as “UCON”), thus they can be easily recovered from aqueous solution just heating above its lower critical solution temperature. Phase diagrams for UCON – Sulfate Salt aqueous two-phase systems (ATPS) have been obtained experimentally in the temperature range 273.15–308.15 K by analysis of the equilibrium phases. The binodal curves and tie-lines have been correlated using suitable methods from the literature. The effect of temperature and the cation used in the Sulfate Salt (sodium, potassium, ammonium) are discussed. Temperature increases the heterogeneous region size while increases the polymer concentration in the polymer-rich phase and reduces the Salt concentration in the Salt-rich phase. This effect produces the phase inversion at high temperatures. The cation ability for phase splitting in these ATPS increases with the (more negative) Gibbs energy of hydration of the cation: Na+ > K+ > NH4+.
Palaniappan Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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Methyl triphenylphosphonium permanganate as a novel oxidant for aniline to polyaniline-manganese(II, IV) oxide: material for high performance pseudocapacitor
Journal of Solid State Electrochemistry, 2018Co-Authors: Susmitha Uppugalla, Rajender Boddula, Palaniappan SrinivasanAbstract:In this work, organic-inorganic composite materials of polyaniline and manganese oxide were synthesized and investigated their electrochemical performance. This composite material was prepared by oxidizing aniline with methyl triphenylphosphonium permanganate as a novel organic oxidant via aqueous, emulsion, and interfacial polymerization pathways. This process led to the formation of polyaniline-Sulfate Salt (PANI-SA-Mn_5O_8). Formation of polyaniline-Sulfate Salt was confirmed from FT-IR, EDAX, and XRD results. Formation of Mn_5O_8 was supported by XRD spectrum. PANI-SA-Mn_5O_8 prepared via emulsion polymerization pathway was obtained in porous nanorod morphology with high conductivity (9.4 S cm^−1) compared to that of the other sample prepared via interfacial pathway (1.7 S cm^−1). Whereas, aqueous polymerization pathway resulted in sheet-like morphology with a conductivity of 0.8 S cm^−1. These composites were used as pseudocapacitive electrode materials. Electrochemical characterization (cyclic voltammetry, charge-discharge, and electrochemical impedance measurement) showed that composite prepared via emulsion polymerization pathway gave better electrochemical performance, and showed good cycling behavior.
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Methyl triphenylphosphonium permanganate as a novel oxidant for aniline to polyaniline-manganese(II, IV) oxide: material for high performance pseudocapacitor
Journal of Solid State Electrochemistry, 2017Co-Authors: Susmitha Uppugalla, Rajender Boddula, Palaniappan SrinivasanAbstract:In this work, organic-inorganic composite materials of polyaniline and manganese oxide were synthesized and investigated their electrochemical performance. This composite material was prepared by oxidizing aniline with methyl triphenylphosphonium permanganate as a novel organic oxidant via aqueous, emulsion, and interfacial polymerization pathways. This process led to the formation of polyaniline-Sulfate Salt (PANI-SA-Mn5O8). Formation of polyaniline-Sulfate Salt was confirmed from FT-IR, EDAX, and XRD results. Formation of Mn5O8 was supported by XRD spectrum. PANI-SA-Mn5O8 prepared via emulsion polymerization pathway was obtained in porous nanorod morphology with high conductivity (9.4 S cm−1) compared to that of the other sample prepared via interfacial pathway (1.7 S cm−1). Whereas, aqueous polymerization pathway resulted in sheet-like morphology with a conductivity of 0.8 S cm−1. These composites were used as pseudocapacitive electrode materials. Electrochemical characterization (cyclic voltammetry, charge-discharge, and electrochemical impedance measurement) showed that composite prepared via emulsion polymerization pathway gave better electrochemical performance, and showed good cycling behavior.
Geert De Schutter - One of the best experts on this subject based on the ideXlab platform.
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The role of Ca(OH)2 in Sulfate Salt weathering of ordinary concrete
Construction and Building Materials, 2016Co-Authors: Zanqun Liu, Dehua Deng, Geert De Schutter, Le HouAbstract:Abstract In the present paper, a micro-analysis of Sulfate Salt weathering of calcium sulfoaluminate (CSA) cement paste and concrete was conducted to offer reference values and to elucidate the Sulfate Salt weathering of ordinary concrete. The test results showed that Na2SO4 crystals could be clearly identified in CSA cement paste and concrete, causing the failure of the paste and concrete in the evaporation zone. Based on the surface physicochemical theory of crystallization in a pore, a solution film between the pore wall and the Salt crystal causes crystal growth and can be formed due to the inert relationship between Sulfates and CSA cement hydration products without the effect of Ca(OH)2. However, after the inevitable chemical reaction between the Sulfates and hydration products of Portland cement due to the existence of Ca(OH)2, the solution film is not formed, and Na2SO4 crystallization cannot occur in the Portland cement concrete.
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The comparison between Sulfate Salt weathering of portland cement paste and calcium sulfoaluminate cement paste
2015Co-Authors: Zanqun Liu, Dehua Deng, Geert De SchutterAbstract:In this paper, the damage performances of Sulfate Salt weathering of Portland cement paste and calcium sulfoaluminate (CSA) cement paste were compared according to authors' previous studies. It was found that the evaporation zone of speciments partially immersed in 10% Na2SO4 solution were both severely deteriorated for Portland cement and CSA cement. However, the differences were more significant: (1) the CSA cement paste were damaged just after 7 days exposure compared to the 5 months exposure of Portland cement paste under the same exposure condition of RH 60% and 20°C; (2) the cement paste specimen was split into several pieces along the shrinkage cracks, and the damaged CSA cement paste consisted of a detachment of successive paste layers; (3) gypsum and ettringite were identified in the Portland cement paste and attributed to the paste failure mechanism, however sodium Sulfate crystals were clearly observed in the detached paste layers. According to the comparison the so-called Sulfate weathering of Portland cement concrete was discussed.
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Does concrete suffer Sulfate Salt weathering
Construction and Building Materials, 2014Co-Authors: Zanqun Liu, Dehua Deng, Geert De SchutterAbstract:Abstract Due to several similarities in deterioration behavior between concrete and other porous materials, Sulfate Salt weathering is regularly considered to be the degradation mechanism causing the concrete deterioration in evaporation zone of partially buried concrete elements in the Sulfate environment. This issue has received increasing attention in recent years. However, according to an extensive literatures review on long term field and laboratory tests in this paper, the experimental results are clearly illogical and contradict with the classic theory of Salt weathering of porous materials, such as (1) the Sulfate crystals cannot be identified by means of micro-analysis methods in the damaged concrete as direct evidences for Sulfate crystallization in concrete; (2) concrete is susceptible to deterioration in a high RH environment; (3) a mere change of cement compositions shows significant influence on concrete damage, however concrete damage is immune to pore structure change; and (4) the damaged concrete part does not contain the highest Salt content, and so on. Instead, the experimental results support that the chemical Sulfate attack should be still the mechanism causing the concrete deterioration. Therefore, an adequate understanding of deterioration mechanism of concrete in the evaporation zone of partially buried concrete elements is quite urgent. In this paper, several issues aimed at the contradictions deduced from field and laboratory tests are proposed to attempt to seek the truth of Sulfate Salt weathering of concrete.
Vaidya Jayathirtha Rao - One of the best experts on this subject based on the ideXlab platform.
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Efficient, convenient and reusable polyaniline-Sulfate Salt catalyst for the synthesis of quinoxaline derivatives
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Chiguru Srinivas, Chebolu Naga Sesha Sai Pavan Kumar, Vaidya Jayathirtha Rao, S. PalaniappanAbstract:Biologically important quinoxaline derivatives were prepared in excellent yields using very low amount of reusable polyaniline-Sulfate Salt catalyst from various 1,2-dicarbonyls and aromatic 1,2-diamines. This methodology is also very much useful for the synthesis of new quinoxaline derivative using sterically hindered diamine.
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Polyaniline-Supported Sulfuric Acid Salt as a Powerful Catalyst for the Protection and Deprotection of Carbonyl Compounds
Synlett, 2003Co-Authors: S. Palaniappan, Chandrasekaran Saravanan, P. Narender, Vaidya Jayathirtha RaoAbstract:Structurally different carbonyl compounds were converted into their corresponding cyclic acetals using polyaniline-Sulfate Salt as catalyst in dry toluene in excellent yield. In turn, useful deacetalization in aqueous medium was demonstrated. Chemoselective protection of carbonyl compounds was also demonstrated. The advantages of the polyaniline-Sulfate Salt are ease of preparation and handling, stability, reusability and activity.
