RING SUBSTITUENT EFFECTS ON DECYLPYRIDINIUM BROMIDE MICELLIZATION

Micellar aggregation numbers of decylpyridinium bromide and 18 structurally related surfactants were determined by conventional light scattering in 0.5 m NaBr and/or 0.5 m NaCl. A few measurements were also made in 0.5 m HBr and in 0.5 m HCl. Two trends were observed. The attachment of a methyl or an ethyl group to the pyridinium ring lowered the aggregation number. Replacement of an alkyl group on the ring with the corresponding alkanol group raised it. In a number of cases, the contribution of a ring substituent to the effective dielectric constant in the Stern layer seems to be a factor in determining micelle size. © 1990.