Faculty Publications
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Item Biodegradability of PMMA blends with some cellulose derivatives(2006) Bhat, D.K.; Muthu, M.S.High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA-CA, and PMMA-CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA-CA and PMMA-CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP. © Springer Science+Business Media, Inc. 2006.Item N and p doped poly(3,4-ethylenedioxythiophene) electrode materials for symmetric redox supercapacitors(2007) Bhat, D.K.; Muthu, M.S.A symmetric redox supercapacitor has been fabricated based on n and p doped Poly(3,4-ethylenedioxythiophene)(PEDOT) coated on stainless steel (SS) electrodes. The characterization and performance of the supercapacitor has been studied by FTIR, Cyclic Voltammetry and AC Impedance spectroscopy. The supercapacitor showed a maximum specific capacitance of 121 F g-1 at a scan rate of 10 mV s-1. The time constant calculated for the supercapacitor through the active-reactive power behavior measurement was 12 milliseconds indicating the suitability of the system for efficient use at low frequency range. © 2007 Springer Science+Business Media, LLC.Item Preparation and characterization of an all solid supercapacitor based on polyaniline-Al2O3 layer on aluminium alloy-Al-2024(2007) Muthu, M.S.; Bhat, D.K.The characteristics of an all solid state supercapacitor based on polyaniline (Pani)-Al2O3 coating on aluminium alloy 2024 (Al-2024) surface prepared by the constant current method have been investigated. Three stages are observed in the potential- electrolysis time relation for the simultaneous preparation of the dielectric layer and the conducting polymer on the aluminium foil. The deposition of polyaniline film has been confirmed by cyclic voltammetry. The solid state capacitor has been studied by AC impedance spectroscopy and the capacitive behaviour of the cell is discussed in terms of Nyquist plots, complex capacitance and complex power. The study revealed that the capacitor has comparatively good capacitance, ranging from 450 to 600nF/cm2, a low time constant and also very low resistance. The normalized reactive power, |Q|/|S| and active power |P|/|S| versus frequency plot for the solid state capacitor allow an overview of the whole frequency behaviour of the supercapcitors, ranging from a pure resistance at high frequency to a pure capacitance at low frequency. When a capacitor is used as a source stiffening capacitor and is buffering the supply by delivering initial current, a lower RC time constant allows delivering significantly more current. So this type of solid-state capacitor can be used for the DC-DC converter modules.Item Activated carbon-polyethylenedioxythiophene composite electrodes for symmetrical supercapacitors(2008) Muthu, M.S.; Bhat, D.K.A symmetrical (p/p) supercapacitor has been fabricated by making use of activated carbon (AC)-poly-ethylenedioxythiophene (PEDPT)-composite electrodes for the first time. The composite electrodes have been prepared via electrochemical deposition of ?-napthalenesulphonate doped PEDPT onto AC electrodes. The characteristics of the electrodes and the fabricated supercapacitor have been investigated using cyclic voltammetry (CV) and AC impedance spectroscopy. The electrodes show a maximum specific capacitance of 158 Fg-1 at a scan rate of 10 mV s_1. This indicates that the in situ electro-polymerization of ethylenedioxythiophene (EDPT) onto AC could improve the performance of carbon electrodes for use in supercapacitors. © 2007 Wiley Periodicals, Inc.Item Molecular interactions of polyvinylpyrrolidone and cellulose acetate butyrate solutions in dimethylformamide(2008) Muthu, M.S.; Bhat, D.K.; Renganathan, N.G.The ultrasonic velocity, density, and viscosities of polyvinylpyrrolidone (PVP) and cellulose acetate butyrate (CAB) solutions in dimethylformamide (DMF) have been measured in the temperature range, 303K-323 K. Using these data, free energy of mixing, solvation number and different polymer-solvent interaction parameters for the solution systems have been calculated to know the presence of molecular interactions in the system. The trends in the variation of the solution property parameters indicate the existence of positive molecular interactions between the polymer and the solvent in solutions. The results also show the presence of higher degree of interaction between PVP and DMF in solution compared to CAB and DMF.Item Molecular interactions of polymethyl methacrylate and polyethyeleneglycol solutions in tetrahydrofuran(2008) Muthu, M.S.; Bhat, D.K.The ultrasonic velocity, density and viscosities of the polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) solutions in tetrahydrofuran (THF) have been measured in the temperature range 293-313K. Using these data, free energy of mixing, solvation number and different polymer-solvent interaction parameters for the solution systems have been calculated to know the presence of molecular interactions in the system. The trends in the variation of the solution property parameters indicate the existence of positive molecular interactions between the polymer and the solvent in solutions. The results also show the presence of higher degree of interaction between PEG and THF in solution compared to PMMA and THF.Item Miscibility of poly(methylmethacrelate) and cellulose acetate butyrate blends in dimethyl formamide(2008) Muthu, M.S.; Bhat, D.K.The miscibility of poly(methylmethacrelate) (PMMA) and cellulose acetate butyrate (CAB) blends in dimethyl formamide (DMF) have been investigated by viscosity, density, refractive index and ultrasonic velocity studies. The polymer-solvent and blend-solvent interaction parameters and heat of mixing have been calculated using the viscosity, density and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in dimethyl formamide in the entire composition range between 303-323 K. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and CAB blends in DMF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. SEM images also supported the miscibility of blends.Item LiClO4 doped cellulose acetate as biodegradable polymer electrolyte for supercapacitors(2008) Muthu, M.S.; Bhat, D.K.The possibility of producing a biodegradable polymer electrolyte based on cellulose acetate (CA) with varied concentration of LiClO4 for use in supercapacitors has been investigated. The successful doping of the CA films has been analyzed by FTIR and DSC measurements of the LiClO4 doped CA films. The ionic conductivity of the films increased with increase in salt content and the maximum ionic conductivity obtained for the solid polymer electrolyte at room temperature was 4.9 × 10-3 ?-1for CA with 16% LiClO4. The biodegradation of the solid polymer electrolyte films have been tested by soil burial, degradation in activated sludge, and degradation in buffer medium methods. The extent of biodegradation in the films has been measured by AC Impedance spectroscopy and weight loss calculations. The study indicated sufficient biodegradability of the materials. A p/p poly-pyrrole supercapacitor has been fabricated and its electro-chemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 90 F g-1 and a time constant of 1 s. © 2008 Wiley Periodicals, Inc.Item Miscibility of polymethylmethacrylate and polyethyleneglycol blends in tetrahydrofuran(2009) Muthu, M.S.; Bhat, D.K.; Renganathan, N.G.The miscibility of polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran. (THF) has been investigated by viscosity, density, refractive index, and ultrasonic velocity studies. Various interaction parameters such as polymer-solvent and blend-solvent interaction parameters and heat of mixing have been calculated using the viscosity, density, and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in THF in the entire composition range. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and PEG blends in THF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. © 2008 Wiley Periodicals, Inc.Item Polyvinyl alcohol-polystyrene sulphonic acid blend electrolyte for supercapacitor application(2009) Muthu, M.S.; Bhat, D.K.A new polymer blend electrolyte based on poly vinyl alcohol and poly styrene sulphonic acid has been studied as an electrolyte for supercapcitors. A carbon-carbon supercapacitor has been fabricated using this electrolyte and its electrochemical characteristics and performance have been studied. The conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. The real and imaginary parts of the electrical modulus of samples show a long tail feature, which can be attributed to high capacitance of the material. The super capacitor showed a fairly good specific capacitance of 40 F g- 1 and a time constant of 5 s. © 2008 Elsevier B.V. All rights reserved.