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-methoxya niline) backbone by the chiral (+)-CSA(-) dopant anion leading to optically active POMA.(+)-HCSA emeraldine salts. The salts obtained from both high m olecular weight (M-w = 144000 Da) and low molecular weight (M-w = 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 (Delta = 130 n m) over 48 h which is attributed to slow de-aggregation of the polymer chai ns. Chiral induction into the poly(o-methoxyaniline) chains is much slower than for the analogous acid doping of the parent polyaniline emeraldine bas e, due to steric hindrance to polymer rearrangement by the methoxy ring sub stituent.