Amino Acid-Containing Phase-Selective Organogelators: A Water-Based Delivery System for Oil Spill Treatment

The
simple structural modification of replacing a terminal carboxylic
acid with a primary amide group was found to lower the minimum gelation
concentration (MGC), by at least an order of magnitude, for a series
of N-lauroyl-l-amino acid phase-selective
organogelators in decane. The amide-functionalized analogue N-lauroyl-l-alanine-CONH2 was demonstrated
to gel a broad range of solvents from diesel to THF at MGCs of 2.5%
w/v or less, as well as to produce gels with a higher thermal stability
(ca. 30 °C) and enhanced mechanical properties
(5 times increase in complex modulus), compared to the carboxylic
acid analogue, N-lauroyl-l-alanine-COOH.
These improved properties may be due to the additional hydrogen bonding
in the primary amide analogue as revealed by SCXRD. Most significantly
for this study, the introduction of the primary amide functionality
enabled N-lauroyl-l-alanine-CONH2 to form a self-assembled fibrillar network in water. The aqueous
network could then actively uptake and rapidly gel decane, diesel,
and diluted bitumen (“dilbit”) with MGCs of 2.5% w/v
or less. This aqueous delivery method is advantageous for oil-remediation
applications as no harmful carrier solvents are required and the gel
can be easily separated from the water, allowing the oil to be recovered
and the gelator recycled.