Ian D. Norris

Facile preparation of optically active polyanilines via the in situ chemical oxidative polymerisation of aniline

Abstract Optically active polyaniline in the non-doped emeraldine oxidation state and as the polymer doped with HCl have been synthesised via the facile in situ deposition of films from an aqueous solution of aniline undergoing oxidative polymerisation. Films of optically active polyaniline doped with (+)- or (−)-10-camphorsulfonic acid (PAn.HCSA) were first deposited from a solution of aniline by ammonium persulfate in the presence of (+)- or (−)-HCSA. Their UV–visible and circular dichroism (CD) spectra suggest significant structural differences to PAn.HCSA salts prepared electrochemically. De-doping of the in situ deposited films with aqueous NH 4 OH gave optically active emeraldine base films, which could be re-doped with HCl vapour or 1.0 mol dm −3 aqueous HCl to generate optically active PAn.HCl films with retention of polymer configuration.

Preparation of chiral conducting polymer colloids

Abstract A novel method for the electrochemical synthesis of chiral conducting polyaniline (PAn) colloids has been developed, via the potentiostatic (+0.9V vs Ag /AgCl) polymerisation of aniline in the presence of either (1R)-(−)-10-camphorsulfonic acid ((−)- HCSA) or (1S)-(+)-10-camphorsulfonic acid ((+)-HCSA). The electrosynthesis was performed under hydrodynamic conditions in an electrochemical flow cell using polyethylene oxide as a stabiliser. The optical activity of the colloidal polyaniline dispersion was established by circular dichroism (CD) spectroscopy. Visible region CD bands were observed at ca. 420 run and were attributed to the macroasymmetry of the polyaniline salt chains. Mirror image CD spectra were obtained for colloids grown in the presence of (+)- or (−)-HCSA, suggesting enantioselectivity during colloidal salt formation.

Electrochemical Actuator Devices Based on Polyaniline Yarns and Ionic Liquid Electrolytes

We report the development of conducting polymer electrochemical linear actuators from ionic liquids (as electrolytes) and polyaniline yarns and hollow fibres (as electrode materials). With a yarn-in-fibre configuration, these actuators were simple to fabricate and allowed two-electrode operation without a reference electrode. Typical electromechanical actuation behavior of expansion, with force decrease, and contraction, with force increase, during charge injection and removal has been realized for these actuators. Stress generation of these actuators was 0.42–0.85 MPa, which exceeds that of skeletal muscle (0.1–0.5 MPa). Practical application of these actuators has been successfully demonstrated by using the electrochemical actuation of a yarn-in-fibre actuator to drive a cantilever object. Importantly, this yarn-in-fibre configuration would allow the combination of an appropriate number of yarns as the actuation electrode to accomplish the mechanical task, depending on the weight of the object.

Properties of chiral polyaniline in various oxidation states

Abstract Optically active polyaniline has been prepared as the conducting emeraldine salts PAn.(+)-HCSA and PAn.(−)-HCSA (HCSA = camphorsulphonic acid). We now report the preparation and chiroptical properties of optically active polyaniline in the following redox and pH states: leucoemeraldine base, emeraldine base, pernigraniline base and pernigraniline salt. These new chiral materials were obtained via the chemical reduction or oxidation of optically active PAn.(+)-HCSA or via de-doping with NH4OH. The reversibe generation of these novel optically active materials is of significance for potential applications.

Chiral Induction in the Acid Doping of Poly(o-methoxyaniline)

The acid doping of the emeraldine base form of poly(o-methoxyaniline) (POMA) with 0.10 mol dm–3 (+)-(1S)-camphor-10-sulfonic acid (HCSA) in dimethyl sulfoxide solvent causes the induction of chirality in the poly(o-methoxyaniline) backbone by the chiral (+)-CSA– dopant anion leading to optically active POMA·(+)-HCSA emeraldine salts. The salts obtained from both high molecular weight (Mw = 144000 Da) and low molecular weight (Mw = 31000 Da) emeraldine base precursors exhibit a well defined high wavelength polaron absorption band consistent with a ‘compact coil’ conformation. In the high molecular weight case, this band undergoes a large red shift (Δ = 130 nm) over 48 h which is attributed to slow de-aggregation of the polymer chains. Chiral induction into the poly(o-methoxyaniline) chains is much slower than for the analogous acid doping of the parent polyaniline emeraldine base, due to steric hindrance to polymer rearrangement by the methoxy ring substituent.

High Flux Polyamide Composite Hollow Fiber Membranes for Reverse Osmosis Applications

High flux composite hollow fiber membranes for brackish water desalination based on the interfacial polymerization of a cross-linked polyamide salt rejecting layer onto a semi-permeable hollow fiber support have been developed. These hollow fiber membranes exploit the advantages of using a thin-film composite reverse osmosis membrane (higher flux and salt rejection) with the higher surface area/volume ratio of hollow fiber membrane elements. The composite hollow fiber membranes were prepared by coating a polysulfone hollow fiber with a polyamide salt rejecting layer based on the interfacial polymerization reaction between m-phenylenediamine and trimesoyl chloride/isophthaloyl dichloride. The RO figures-of-merit of these composite polyamide hollow fiber membranes were evaluated for the desalination of a synthetic brackish water feed (2,000 ppm NaCl) at 225 psi over a 60 hour period. After an initial break-in period in which the flux declined 30% due to membrane compaction, the stabilized RO figures-of-merit for these hollow fiber membranes were a water flux of 280 L/m 2 ·day and a salt rejection of 99.1%. Based on the water flux and packing density of the membrane, it is estimated that the stable production of potable water of a hollow fiber membrane element containing these composite membranes will be between 20 and 30% greater than that of a similarly sized spiral wound brackish water membrane element.