Micellar aggregation behavior at low ionic strength of cyclic acetal-type cationic surfactants containing the 1,3-dioxolane moiety

Aggregation studies in water of several cationic acetal-type surfactants having varied hydrophobic chains, [(2-alkyl-1,3-dioxolan-4-yl)methyl]trimethylammonium bromides (C-n-D-TAB; where C-n = C9H19, C11H23, C13H27), have been performed by means of dynamic light scattering in the 0.015-0.32 M NaBr concentration range over the temperature limits of 25-45 degrees C. The aggregation parameters (translational diffusion coefficient of micelle (D-0), hydrodynamic radius (R(h)), ionization fraction (alpha), and aggregation number (n)) have been determined and discussed with respect to the parameters of the ''classical'' alkyltrimethylammonium bromides (C-n-TAB). Additionally, the effect of diastereoisomerism upon surfactant aggregation has been characterized for the trans- and cis-[(2-tridecyl-1,3-dioxolan-4-yl)methyl]trimethylammonium (C-13-D-TAB), (2-hydroxyethyl)dimethylammonium (C13D-HEAB), and triethylammonium (C-13-D-TEAB) bromides. Accordingly, the 1,3-dioxolane ring configurations and the size of the head groups do not involve noticeable diastereomeric discrimination in the self-assembling abilities. Because the studied cationic acetal-type surfactants contain a 1,3-dioxolane unit (D), they are an acid hydrolyzable type of chemodegradable surfactant, which is analogous to C-n-TAB in terms of the micellar aggregation characteristics.