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.