Synthesis and self-assembly studies of glycoside surfactants and chromonics / Faramarz Aliasghari Sani
This thesis focused on the synthesis and self assembly studies of compounds involving carbohydrates. Two different types of materials were studied, i.e. surfactants and chromonics. Physical investigations of the compounds were conducted by TGA, DSC, OPM, UV-Vis spectroscopy, 1H NMR and surface te...
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| 總結: | This thesis focused on the synthesis and self assembly studies of compounds involving
carbohydrates. Two different types of materials were studied, i.e. surfactants and
chromonics. Physical investigations of the compounds were conducted by TGA, DSC,
OPM, UV-Vis spectroscopy, 1H NMR and surface tension measurements. Sugar-based
surfactants are interesting compounds for pharmaceutical and personal care products.
Current commercially available surfactants such as alkyl poly glucoside surfactants
(APGs) are prepared from low miscibility of sugars and fatty alcohols. In order to
solve the miscibility problems of the starting materials, homogenizers are required.
This, however, leads to impurities in products, which affects the use of the surfactant
for life science applications. Therefore, this work focused on an economic preparation
of pure glycoside surfactants. The synthesis approach applied a separation of
glycosides and a coupling of sugar and fatty alcohols with different length and chain
branching by click chemistry. Twenty one alkyl triazole glycoside surfactants (ATGs)
were prepared with more than 80% yield. Twelve of these were anomeric pure
products (>95% purity) and nine were technical products of α/ anomeric mixtures.
The materials were characterized for their liquid crystal behaviours. Contact
penetration studies showed a whole range of lyotropic phases from lamellar to cubic
and hexagonal. ATGs’ CMCs were found to be lower than those of APG surfactants.
An increase in their chain length meant a decrease in CMC values. Hence these
materials could be identified for oil-based surfactants applications.
Chromonics or lyotropic chromonic liquid crystals (LCLCs) are formed by the selfassociation
of aromatic disk-shaped molecules with hydrophilic groups at the
periphery in aqueous solutions. The chromonics are assembled from π-π interactions
of the aromatic cores. This leads to aggregates based on stacking of the molecules.
Most chromonic molecules are based on ionic structures. The research embraced the
synthesis and assembly studies of non ionic chromonics consisting of triphenylenebased
units surrounded by glycosides. The key point for the synthesis of triphenylene
core was oxidative trimerization of veratrole and guaiacol under anhydrous conditions
in the presence of ferric chloride. A symmetric compound with six sugars and an
asymmetric one with three sugar units were synthesized. The materials were of purity
over 95% and more than 75% yield. Due to the anisotropic effect on the aromatic ring
on 1H NMR, the chemical shift on the aromatic ring changed when the concentration
was increased. This means the materials formed aggregation and enabled the
determination of critical aggregation concentrations (CAC). Moreover, this property
also showed temperature dependency. At higher concentrations and under examination
by polarizing light microscopy, the chromonic exhibited liquid crystalline properties
(Col phase). |
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