Partial molal volume and light scattering studies on certain alkyltrimethylammonium bromides, and the effect of added 1-alkanols

Abstract

An examination of the volumetric properties of alkyltrimethylammonium bromides at and below the critical micelle concentration shows that the partial molal volume (v¯) of the monomer increases with increasing alkyl chain length. Micelle formation is accompanied by an increase inv¯. The addition of aliphatic alcohols to dodecyltrimethylammonium bromide solutions brings about an increase inv¯, as well as the apparent molecular weight of the micelle. The micelles become larger and nonspherical as the alcohol concentration is increased, but at higher concentration a reduction in size is found. The addition of alcohols is considered to affect the micellar stability by changing the composition and dielectric constant of the environment.