Syed Ashraf

Compositional effects of PEDOT-PSS/single walled carbon nanotube films on supercapacitor device performance

Supercapacitors are promising energy storage and power output technologies due to their improved energy density, rapid charge-discharge cycle, high cycle efficiency and long cycle life. Free standing poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate)/single walled nanotube films have been characterised by scanning electron microscopy, Raman spectroscopy and thermo-gravimetric analysis to understand the physical properties of the films. Films with varying compositions of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) and single walled nanotubes were compared by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge/discharge to understand their electrochemical properties. A comparison of the results shows that having single walled nanotubes dispersed throughout the polymer matrix increase the capacitance by 65% and the energy density by a factor of 3 whilst achieving good capacity retention over 1000 cycles.

Influence of the chiral dopant anion on the generation of induced optical activity in polyanilines

Abstract Emeraldine base (EB) is doped with (1S)-(+)-3-bromocamphor-10-sulfonic acid and a novel chiral acrylamidesulfonic acid (4) in NMP and DMF solvents to give new optically active polyaniline salts (PAn.HA). The conjugate base anions (A − ) of these chiral dopants (as with the previously studied (+)-camphor-10-sulfonic acid, HCSA) contain SO 3 − and carbonyl (C=O) groups that may maintain the polyaniline chains in a preferred one-sense helical screw via simultaneous electrostatic and H-bonding. Optically active polyaniline salts are also produced via analogous doping of EB (in NMP or DMF) with the chiral dicarboxylic acids (+)- or (−)-tartaric acid and O,O′-dibenzoyl- d -tartaric acid, which possess quite different structural motifs to HCSA. A common feature of all the dopants successful in generating optically active polyaniline salts is their bidental nature, allowing attachment of the dopant to the polymer backbone at two places simultaneously.

Bulk electropolymerization of alkylpyrroles

Abstract New larger-scale (10 g monomer in 500 cm 3 ) methods for the electropolymerization of alkylpyrroles in quantity have been developed. These methods offer the advantage of electropolymerization with fractionation in a single step. Galvanostatic, potentiostatic and potentiodynamic methods have been considered. 3-Octadecylpyrrole was electrochemically synthesized in dichloromethane. The use of other solvent systems, namely dichloromethane/acetonitrile, carbon tetrachloride/dichloromethane or tetrahydrofuran/acetonitrile mixtures, has also been considered. Furthermore, the new copolymer of 3-octadecylpyrrole with pyrrole was successfully grown in dichloromethane/acetonitrile medium. The investigations were extended to 3-octylpyrrole, which was successfully electropolymerized. The products are conductive, some are electroactive and many can be dissolved in common organic media. The solubilities (some in excess of 50% by weight) of these polymers and their conductivities (as high as 31.4 S cm −1 ) are reported. The yields and conductivities are dependent upon the solvent system and electrolyte used for electrosynthesis. The solvent system used for electrosynthesis also affected the solubility of the polymers produced. For cast films, the electroactivity depended not only upon the polymer but also upon the casting solvent.

Factors controlling the induction of optical activity in chiral polyanilines

Abstract A systematic investigation is reported of the effect of the following factors on the ability togenerate optically active polyanilines: (i) stenc and electronic properties of aniline ring substituents (eg. H, Me, MeO), (ii) the nature of the chiral dopant (chiral sulphonic and tartaric acids), and (iii) the solvent.

Incorporation of various counter-ions during electropolymerization of 3-methylpyrrole-4-carboxylic acid

Incorporation of perchlorate (ClO4−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−) and p-toluene sulfonate (PTS−) into poly(3-methylpyrrole-4-carboxylic acid) (PMPC) during electropolymerization was considered in this work. Potentiodynamic, potentiostatic and galvanostatic polymerization methods were employed, and the corresponding cyclic voltammograms, chronoamperograms and chronopotentiograms were recorded. Preliminary characterization of the resultant polymers was carried out using scanning electron microscope, energy dispersive X-ray analysis and cyclic voltammetry after growth.

Investigations into the Use of Poly (3-Methylpyrrole-4-Carboxylic Acid) Coated Silica as a Chromatographic Stationary Phase

Abstract Poly (3-methylpyrrole-4-carboxylic acid) (PMPC) was coated on to a silica support for use as an HPLC stationary phase. Reversed phase anion exclusion and cation exchange chromatographic behaviour have been characterised using a group of test compounds. The precominant mode of interaction was found to be dependent on the eluent conditions. Separation of various compounds was carried out and the applicability of this stationary phase for protein secarations was investigated.

Facile Synthesis of a Chiral Ionic Liquid Derived from 1-Phenylethylamine

A simple route is described to enantiomerically pure ionic liquids derived from (+)- and (–)-1-phenylethylamine. These very low melting point (–42°C) ionic liquids, containing the bis(trifluoromethylsulfonylimide) anion, possess a wide electrochemical potential window between –2.0 and +2.0 V (versus Ag|AgCl). They show chiral discrimination between the enantiomeric forms of Mosher’s salt, suggesting their potential as media for electrochemical asymmetric syntheses or chiral chromatography.

Electropolymerization of 4-(3-pyrrolyl)-4-oxobutyric acid by in situ potentiodynamic pre-reduction/oxidation

Abstract Electrochemical polymerization of 4-(3-pyrrolyl)-4-oxobutyric acid and its copolymerization with pyrrole produces electroactive polymers and copolymers, respectively. This study highlights the advantages to be gained by using transient potential waveforms for production of polymer materials.

Chemical polymerization of 3-methylpyrrole-4-carboxylic acid

Abstract 3-Methylpyrrole-4-carboxylic acid has been polymerized chemically. The polymer was compared with that prepared electrochemically using elemental analysis, FTi.r. and SEM.