ELSEVIER PII: S0032-3861 (96)00835-X Polymer Vol. 38 No. ll, pp. 2627-2631, 1997 ~ 1997 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0032-3861/97/$17.00 + 0.00 Influence of the chiral dopant anion on the generation of induced optical activity in polyanilines Syed A. Ashraf, Leon A. P. Kane-Maguire*, Mir Reza Majidi, Stephen G. Pyne and Gordon G. Wallace Intelligent Polymer Research Laboratory, Institute for Molecular Recognition, University of Wollongong, Northfields Ave., Wollongong, NSW 2522, Australia (Received 14 June 1996, revised 21 August 1996) Emeraldine base (EB) is doped with (lS)-(+)-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 SO3 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-o-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. © 1997 Elsevier Science Ltd. (Keywords: polyaniline salts; induced optical activity; chiral dopant) INTRODUCTION We recently reported 1'2 the first synthesis of optically- active polyaniline salts of type (1) via the enantioselective electropolymerization of the achiral monomer, aniline, in the presence of either (+)- or (-)-camphorsulfonic acid (HCSA). Subsequently, we have shown that such optically active polyaniline salts can also be readily generated in solution 3 and as films4 by the acid doping of emeraldine base (EB) with (+)- or ~-)-HCSA in various organic solvents. Havinga et alF have also recently produced an optically active polyaniline salt film via the doping of EB with (+)-HCSA in m-cresol solvent. H H CSA- (1) We postulated 1-4 that the observed macromolecular asymmetry arose from the polyaniline chain adopting, at least partially, a preferred one-sense helical screw which was maintained by the enantiomeric CSA- anions +. linking NH and NH centres three dimeric repeating units apart along the polymer chain. Two simultaneous modes of attachment of the chiral anion to the polymer chain were considered essential for enantioselectivity, * To whom correspondence to be addressed namely electrostatic bonding of the CSA- sulphonate +. ion to polyaniline N H centres and H-bonding of the CSA- carbonyl group to NH sites (Scheme 1). In order to test this hypothesis and to throw further light on the factors responsible for the generation of induced optical activity in such doping reactions, we have now examined the acid doping reaction (1) of emeraldine base with a series of other chiral dopant acids (2-6) incorporating different structural motifs. The chiroptical properties of the new chiral polyaniline salts (7) obtained are described. EXPERIMENTAL Materials (1S)-(+)-3-bromocamphor-10-sulfonic acid (2), (+)- and (-)-tartaric acid (Sa, 5b), (+)-O,O'-dibenzoyl-e-tartaric acid (6), N-methylpyrrolidinone (NMP), dimethylsulf- oxide (DMSO) and dimethylformamide (DMF) were purchased from Aldrich Co., Australia, and employed as received. The synthesis of the novel sulfonic acids (3) and (4) has been recently described by some of us 6. Neutral emeraldine base (EB) was prepared using a previously described procedure 7. Doping experiments Doping of this neutral polymer with each of the chiral aci~ (2-6) to generate polyaniline salts of the type (7) was carried out in situ by vigorously shaking 1 mg of solid EB with a 10ml solution of the dopant acid in the appropriate solvent for 15min (dopants POLYMER Volume 38 Number11 1997 2627