posted on 2017-12-30, 00:00authored byMohammed I. Jeraal, Kevin J. Roberts, Ian McRobbie, David Harbottle
There is a notable
lack of published data concerning sodium cocoyl
isethionate despite widespread application in the personal care industry.
A specific homologue, sodium lauroyl isethionate (SLI), was therefore
synthesized, purified by recrystallization, and then subjected to
a detailed physicochemical examination. A purity of 98% was achieved
via repeat recrystallization in methanol. A turbidimetric solubility
analysis was then executed to identify both its crystallizability
and metastable zone width as a function of temperature. Thermogravimetric
analysis yielded decomposition onsets of 330 °C for the purified
SLI. A dynamic vapor sorption study also demonstrated reversibility
in the 2.3% mass gained when it was exposed to sustained humidity
of 87%. Surface tension measurements of purified SLI yielded a critical
micellar concentration (CMC) of 5.4 mM and a plateau surface tension
of 38 mN/m at 20 °C. Both values are lower than the previously
reported values for SLI in water, thus indicating the performance
benefits of purified isethionates in personal care formulations. The
single step synthesis was chlorine-, catalyst-, and solvent-free,
thus improving process efficiency, safety, and throughput over existing
SLI syntheses. The succeeding physicochemical analysis crucially provides
much needed insight into the purification, properties, and performance
of isethionate ester surfactants, all of which are strongly applicable
to their commercial manufacture from biorenewable sources.