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MIT World Peace University

School of Polymer Engineering

The polypyrrole (PPy) films were deposited on vacuum metallized substrates by electro-oxidation of pyrrole monomer. These electrodes were then modified with a range of metal halides having different electronegativities. The modified polypyrrole electrodes were employed to investigate electrocatalytic activity towards methanol electrochemical oxidation by means of cyclic voltammetry in 0.1 M HClO4 as supporting electrolyte. It was found that the electronegativity of the dopant ion incorporated in the PPy film governs the electrocatalytic activity towards methanol oxidation. Among different dopant anions used in the present work, the PPy doped with zirconium chloride gave the highest anodic current of 10 mA cm-2 at the oxidation potential of methanol. Electrical property and the charge created due to doping in the polymers were measured using X-ray photoelectron spectroscopy (XPS) and Electron spin resonance spectroscopy (ESR). Electrocatalytic activity of the modified electrodes was correlated with various factors obtained from different polymer characterization experiments. The results were explained on the basis of the charge-transfer efficiency at the electrode{pipe}electrolyte interface, which was associated with the acceptor state created by the dopant in the semi-conducting polymer. © 2009 Elsevier B.V. All rights reserved.

World University root node

Engineering and Technology

Synthetic Metals

Influence of dopant ions on properties of conducting polypyrrole and its electrocatalytic activity towards methanol oxidation

Composites with polyvinyl chloride (PVC) as major matrix constituent, ethylene vinyl acetate (EVA) as polymeric plasticizer and wood flour (WF) and fly ash (FA) as filler were extruded. Morphology of the samples was studied using scanning electron microscopy (SEM). Morphological study indicated good dispersion of the constituents. Infrared spectroscopy (IR) indicates interaction between EVA and PVC and also between the polymeric matrix and WF. The effect of various constituents on glass transition temperature (Tg) was evaluated using differential scanning calorimetry. Addition of EVA decreased the Tg, whereas Tg was increased due to addition of WF and FA. Study indicated that reduction in Tg on addition of EVA was compensated by increase in Tg due to addition of WF. The contribution of FA to change in Tg was not significant. Resulting composites have Tg close to that of PVC. © 2009 Wiley Periodicals, Inc.

Journal of Applied Polymer Science

Characterization of highly filled wood flour-PVC composites: Morphological and thermal studies

Coatings prepared from polyaniline–nano-TiO2 particles synthesized by in situ polymerization were found to exhibit excellent <a href="https://www.sciencedirect.com/topics/chemistry/corrosion-resistance">corrosion resistance</a> much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10&nbsp;wt% polyaniline prepared with different concentrations of nano-TiO2. The <a href="https://www.sciencedirect.com/topics/chemistry/impedance-spectroscopy">electrochemical impedance spectroscopy</a> was studied at periodic intervals during exposure to hot saline (65&nbsp;°C) conditions for prolonged durations over a period of 90&nbsp;h. The <a href="https://www.sciencedirect.com/topics/chemistry/open-circuit-potential">open circuit potential</a> (OCP) was found to shift with time from −0.38&nbsp;V SCE to more anodic side (−0.2&nbsp;V SCE) much above that of bare steel (−0.5&nbsp;V SCE). The presence of nano-TiO2 was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18&nbsp;wt% nano-TiO2. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nano-size TiO2, redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive.

Electrochimica Acta

Conducting polyaniline–nano-TiO2 composites for smart corrosion resistant coatings

A rapid carbon monoxide detection system was developed with the electrochemical functioncalization of polypyrrole (PPy) with ferrocenylmethyltrimethylammonium iodide (FTMA-I) as a co-dopant exhibits very high sensitivity to ppm levels of carbon monoxide gas and fast recovery under normal dry room temperature conditions. The co-dopant was synthesized mainly to incorporate into PPy electrochemically to modify the properties in order to sense carbon monoxide (CO) gas. The FTMA-I doped PPy exhibited the characteristics oxidation/reduction peaks for ferrocene in its cyclic voltammograms. The modified PPy films deposited on interdigited electrodes gave rapid sensitivity within a second to 300 ppm carbon monoxide gas and good sensitivity factor was observed even at 4 mmol of the functional groups in the polymer for 300 ppm carbon monoxide gas. This material detected the CO gas concentration as low as 100 ppm. © 2008 Elsevier B.V. All rights reserved.

Polypyrrole functionalized with ferrocenyl derivative as a rapid carbon monoxide sensor

Liquid crystalline materials display unique properties, which can be exploited in organic light emitting diodes. Polythiophene model compounds containing phenyl groups linked with azomethine, ester, and alkoxy groups [thiophene-3-alkyloxy benzoyloxy aniline series (N series) and thiophene-3-alkoxy phenoxy amino benzoate series (R Series)] were synthesized. Molecular orbital calculations were performed and the predicted band gaps compared to understand the effects of spacer length and linkage. The experimental photoabsorption characteristics are compared with the theoretically predicted band gap. Photoabsorption and emission studies on N series and R series polymers as the function of polarizer angle suggest that polymers of both series emit polarized light in all base color ranges. The electroemission characteristics of the above-synthesized polymers were also recorded as the function of polarizer angle. The results show that the compounds also emit polarized electroemission, and the EL polarization ratio decreases with the increase of alkoxy chain length for N and R polymers. © 2008 Wiley Periodicals, Inc.

Journal of Polymer Science, Part B: Polymer Physics

Structure-property studies and orientation effects of polythiophenes containing mesogenic side chains

A method for the removal of anionic (sulfonated) dyes from aqueous dye solutions using the chemical interaction of dye molecules with polyaniline is reported. Polyaniline (PANI) emeraldine salt was synthesized by chemical oxidation. Sulfonated dyes undergo chemical interactions with the charged backbone of PANI, leading to significant adsorption of the dyes. This phenomenon of selective adsorption of the dyes by PANI is reported for the first time and promises a green method for removal of sulfonated organics from wastewater. The experimental observations from UV-vis spectroscopy, X-ray diffraction, and conductivity measurements rule out the possibility of secondary doping of polyaniline salt by sulfonated dye molecules. A possible mechanism for the chemical interaction between the polymer and the sulfonated dye molecules is proposed. The kinetic parameters for the adsorption of sulfonated dyes on PANI are also reported. © 2008 American Chemical Society.

School of Mechanical Engineering

Journal of Physical Chemistry B

Adsorption of sulfonated dyes by polyaniline emeraldine salt and its kinetics

Nanofibrous morphology has been observed in ternary blends of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and isotactic polypropylene (PP) when these were melt-extruded via slit die followed by hot stretching. The morphology was dependent on the concentration of the component polymers in ternary blend LDPE/LLDPE/PP. The films were characterized by wide angle X-ray diffraction (XRD), scanning electron microscopy (SEM), and testing of mechanical properties. The XRD patterns reveal that the β phase of PP is obtained in the as-stretched nanofibrillar composites, whose concentration decreases with the increase of LLDPE concentration. The presence of PP nanofibrils shows significant nucleation ability for crystallization of LDPE/LLDPE blend. The SEM observations of etched samples show an isotropic blend of LDPE and LLDPE reinforced with more or less randomly distributed and well-defined nanofibrils of PP, which were generated in situ. The tensile modulusand strength of LDPE/LLDPE/PP blends were significantly enhanced in the machine direction than in the transverse direction with increasing LLDPE concentration. The ultimate elongation increased with increasing LLDPE concentration, and there was a critical LLDPE concentration above which it increased considerably. There was a dramatic increase in the falling dart impact strength for films obtained by blow extrusion of these blends. These impressive mechanical properties of extruded samples can be explained on the basis of the formation of PP nanofibrils with high aspect ratio (at least 10), which imparted reinforcement to the LDPE/LLDPE blend. © 2007 Wiley Periodicals, Inc.

Development of nanofibrous morphology in LDPE/LLDPE/PP blends and its effect on mechanical properties of blend films

This paper reports studies undertaken on 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT). The synthesis of DPT was carried out by the nitration of hexamine based on the lines of reported method with minor modification. DPT was characterized by elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) techniques. Thermal stability of DPT was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal analysis studies revealed that DPT undergoes decomposition at 211 °C. Decomposition of DPT using TG-FTIR indicated the evolution of carbon dioxide, water and oxides of nitrogen as main gaseous products. The electrochemical behavior of DPT was studied using cyclic voltammetric (CV) studies. The experimentally determined sensitivity parameters indicated the insensitive nature of DPT towards external stimuli. The performance parameters of DPT, RDX and HMX have been computed using Linear Output Thermodynamic User Friendly Software for Energetic Systems (LOTUSES) code. The predicted properties of DPT are interesting and important from the point of process technology and/or safety. The work reported in this paper enriches the existing scanty research and development data on one of the key precursor used for synthesis of important high energy materials (HEMs). © 2007 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials

Synthesis, characterization and thermolysis studies on 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT): A key precursor in the synthesis of most powerful benchmark energetic materials (RDX/HMX) of today

3,7-Dinitro-1,3,5,7-tetrazabicyclo-[3,3,1]nonane (DPT) is a key intermediate in the preparation of octahydro-1,3,5,7-tetranitro 1,3,5,7-tetrazocine (HMX), one of the most powerful high-melting explosives. The present investigation focuses on DPT formation during semi-batch and continuous processes. Qualitative and quantitative picture has been brought out to realize the role of DPT in HMX formation. The study reveals that only two thirds of DPT is formed in the continuous process as compared to that of semi-batch process. The calculated final yield of HMX on reaching steady state in the continuous process is comparable to the semi-batch process. This study also illustrates the usefulness in understanding the role of DPT in the final yield of HMX.

Journal of Energetic Materials

Comparative study on the role of DPT on the formation of HMX in semi-batch and continuous process

Polypyrrole (PPy) was modified with ferrocene (Fc) by direct incorporation during polymerization so as to increase its sensitivity for carbon monoxide (CO) gas sensor applications. Synthesis was carried out by chemical oxidative polymerization in the presence of ferrocene using ferric chloride. The presence of these species in PPy was confirmed by different characterization techniques. The CO response measurements were carried out for the sensors fabricated in a surface cell mode with active PPy + Fc films by exposing to CO gas (300 ppm) at room temperature and it was found that the response as well as the recovery characteristics of these materials is very fast and dependent on the film composition. The response factor was found to be maximum for a 1.32 mol% Fc content in the polymer. These various results can be explained on the basis of interaction of CO molecules with Fe atoms of the ferrocene together with charge transfer interaction with the PPy chain. © 2007 Elsevier B.V. All rights reserved.