Development of alkyl triazole glycoside surfactants for water-in-oil emulsification / Ng Su-Han

Ng , Su-Han (2021) Development of alkyl triazole glycoside surfactants for water-in-oil emulsification / Ng Su-Han. PhD thesis, Universiti Malaya.

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Abstract

Fuel-water emulsification is an approach to reduce toxic combustion byproducts from diesel and recycled fuels. Emulsion stability is crucial for commercial viability; hence the development of effective W/O surfactants is needed. In this work, alkyl triazole glycoside (ATG) surfactants were synthesized from renewable materials, namely sugar and fatty acids, and linked by Cu (I) catalysed azide alkyne cycloaddition (CuAAC), a Click reaction. The modular reaction allows structural variations on both antipodes to tune the structure for better W/O stability. Parameters involve the variation of the linker between sugar and hydrophobic domain, branching of the hydrophobic domain via multiple click reactions or branched starting material, and the use of different sized sugar headgroups. Initial investigations on single chained ATGs indicated negligible effect of the linker length on O/W emulsion stability. However, in bistriazole ATGs, the symmetrically branched ATGs had significantly higher CMCs than their asymmetrical counterparts. This is thought to be caused by -stacking interactions. Bistriazole ATGs generally showed improved W/O emulsion stability but exhibited higher Krafft points and a tendency to complex Cu (II) ions. This was not observed for the oleic acid derived mono ATGs. These surfactants combined good W/O emulsion stability with lower Krafft points. Among the approaches, usage of naturally branched derivatives, such as oleic acid, and limiting the number of triazole rings produced ATG surfactants with good emulsion stability and less complications in synthesis and workup.

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