Synthesis of novel surfactants from biomass derivable starting materials and analysis of their properties

This thesis explores the synthesis and properties of novel bioderivable surfactants, focusing
on the hydrophobic components, in an attempt to find replacements for perfluorinated
surfactants. Perfluorinated surfactants have excellent thermal and chemical stability,
excellent surface tension reduction and extreme hydrophobicity and oleophobicity.
However, perfluorinated surfactants are also toxic and persistent in the environment.
Globally, the production and use of perfluorinated surfactants is being phased out due to
regulatory pressures from Europe and the US. Therefore, sustainable replacements for their
varied applications which do not pose a threat to the environment are needed.
Lignocellulosic biomass, specifically from waste biomass so as not to compete with food
production, is an ideal renewable feedstock for sustainable surfactant production. High
density alkanes produced in biofuel research were selected as platforms for the synthesis of
novel surfactants to increase hydrophobicity in comparison to typical linear chain
surfactants.
Novel surfactant hydrophobes were synthesised primarily through aldol condensations to
give branched ketones followed by hydrogenation to produce fatty alcohols. Several
methodologies were attempted to attach a variety of head groups to the hydrophobic
structures to produce a range of surfactants. These include sulfonation of the α,β
unsaturated ketones, amination of the α,β-unsaturated ketones and etherification of
alcohols to produce a poly (ethylene glycol) head group, all of which were unsuccessful. This
lead to the use of an ester link between the head and tail groups which also promotes
biodegradability of the surfactant. Esterification was successfully achieved using an acyl
chloride as an intermediate producing 9 novel compounds with potential to behave as
surfactants.
Standard industry techniques confirmed that all 9 compounds exhibited surfactant
properties and were benchmarked against industrially produced surfactant blends. Analysis
methods included Wilhelmy plate static surface tension method, dynamic surface tension
measurements and dynamic light scattering measurements. From these analysis techniques
the size of the micelles formed was discussed, as well as the speeds at which each surfactant
migrated to a newly formed surface and the critical micelle concentrations (CMC) of each
compound were determined.