Influence of additives and cation chain
length on the kinetic stability of supersaturated catanionic systems,
In a previous study we have shown that the substitution of alkali ions in
common fatty acid soaps by choline as a counterion of biol. origin increases
the soly. of the resp. soaps without lowering the biocompatibility.
Nevertheless, while choline dodecanoate (ChC12), myristate (ChC14), and
palmitate (ChC16) have Krafft points below room temp. or even under 0°,
choline stearate (ChC18) was not sol. below 40°. In the present
contribution we show that an excess of choline hydroxide is able to solubilize
choline stearate at temps. as low as 14°. Furthermore, we compare our
results to those obtained for the sodium and potassium salts of fatty acids,
with molar ratios of base to acid higher than 1:1. In order to elucidate the
solubilization process regarding the different ion binding to the carboxylic
headgroup, we further investigated the effect of different added chloride salts
on the soly. of choline stearate. Our findings indicate that the cation
affinity to the carboxylate headgroup follows the trend Na+ > K+ .mchgt.
Ch+. The results are discussed in terms of hydrolysis of the fatty acids in
combination with Collins' concept of "matching water affinities". As
a feasible application of choline base, we present the sapon. and simultaneous
solubilization of butter as an example of a hardly sol. triglyceride.
Regina Klein, Matthias Kellermeier, Markus Drechsler, Didier Touraud, Werner
Colloids and Surfaces, A: Physicochemical and Engineering
Aspects (2009) 338(1-3), 129-134.