The effect of the presence of salt on the structure of, and
interactions between, zwitterionic micelles has
been studied using radioactive tracer self-diffusion and elastic and
quasi-elastic light scattering.
Intermicellar interactions were found to become significantly more
repulsive in the presence of salt.
Electrostatic interactions calculated from the known micellar
charges do not account for the experimental
results. The origin of those salt-induced repulsive interactions
is discussed with the help of experimental
data about a series of zwitterionic surfactants having polymethylene
intercharge groups of variable length.
An increase of micelle excluded volume by reorientation of the
zwitterionic headgroups was found to be
consistent with both elastic and quasi-elastic light-scattering data
and with their variation with surfactant
molecular structure. It is likely that electrostatic screening by
salt adsorption at the micellar surface
allows more conformational freedom, switching from a zwitterion
orientation parallel to the interface to
a more radial average orientation in the presence of an increasing NaCl
concentration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.