Photoluminescence and photo-redox reactions of poly(2-methoxyaniline-5-sulfonic acid)

The water-soluble fully sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) has been found to photoluminesce in its emeraldine oxidation state, ES(PMAS). Excitation of aqueous solutions at 450-530 nm, near its characteristic absorption band at 473 nm, led to emission at ca. 600 nm (2.1 eV). Calculations incorporating cyclic voltammetric data for ground state PMAS suggest that the photo-generated ES*(PMAS) excited state should be both a very powerful oxidising agent and a strong reducing agent (ca. 2.7 and 1.1 V of oxidising and reducing power, respectively). This prediction has been confirmed from photolysis studies of ES(PMAS) in the presence of the potentially reducible cobalt(III) cations CoCl(NH3)52+, Co(H2O)(NH3)53+ and Co(en)33+. In water, photo-oxidation of the ES(PMAS) to its fully oxidised pernigraniline base PB(PMAS) form was confirmed by UV-visible spectroscopy. In the case of Λ-Co(en)33+ as the acceptor, strong support for the concomitant reduction of the Co(III) complex to the corresponding Co(II) species was obtained from its observed racemisation. Relatively low quantum efficiencies (\u3c3%) were established for these novel, photo-initiated redox reactions. These photo-redox reactions were preceded by a photo-initiated conformational change in the ES(PMAS) polymer from an -€œextended coil-€ to a -€œcompact coil-€ conformation. The presence of added Na+ and NH4+ ions had a marked influence on the nature of the photo-reactions, with Na+ ions retarding the photo-assisted electron transfer, while NH4+ ions prevented the initial conformational change in the ES(PMAS)

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

Poly(2-methoxyaniline-5-sulfonic acid)-surfactant complexes and their redox and solvatochromic behaviour

Novel stoichiometric (1:1) complexes between the anionic conducting polymer poly(2-methoxyaniline-5-sulfonic acid) (PMAS) and a range of cationic ammonium surfactants have been prepared and characterized. The supramolecular PMAS–surfactant complexes are stable in chloroform and ethanol solutions, in which the PMAS moiety adopts an ‘extended coil’ conformation. Thin films of the complexes can be cast onto indium tin oxide-coated glass from these solutions. The application of an appropriate applied potential leads to redox switching of the PMAS from the emeraldine salt form to its pernigraniline and leucoemeraldine oxidation states. Immersion of the PMAS–surfactant films in 1.0 M NaOH causes the PMAS moiety to undergo conversion into a ‘compact coil’ conformation rather than alkaline de-doping to the emeraldine base form. When the PMAS–surfactant complexes are dissolved in polar organic solvents such as N,N-dimethylformamide, N-methylpyrrolidinone, and acetone, they undergo marked solvatochromism, which is interpreted in terms of rearrangement of the PMAS polymer chains from an ‘extended coil’ to a ‘compact coil’ conformation

Influence of added hydrogen bonding agents on the chiroptical properties of chiral polyaniline

The chiroptical properties of optically active polyaniline PAn.(−)-HCSA emeraldine salt (ES) products in NMP are stabilised by the presence of potential H-bonding additives such as l-arginine, l-tyrosine, l-alanine, l-valine, and glycine in the precursor emeraldine base/NMP solution prior to acid doping with (R)-(−)-10-camphorsulfonic acid. The stabilisation, i.e. absence of partial solvent-induced deprotonation of the ESs to emeraldine base is attributed to H-bonding interactions between the amino acids and the precursor emeraldine base

Conductive Electroactive Polymers: Intelligent Polymer Systems

Rapid advances in synthetic polymer science and nanotechnology have revealed new avenues of development in conductive electroactive polymers that take greater advantage of versatile class of materials\u27 unique properties. This third edition of Conductive Electroactive Polymers: Intelligent POlymer Systems continues to provide an in-depth understanding of how to engineer dynamic properties in inherently conducting polymers from the molecular level