Thermotropic and lyotropic liquid crystal behaviour of Amphiphilic mannosides / Melonney Patrick

Melonney , Patrick (2018) Thermotropic and lyotropic liquid crystal behaviour of Amphiphilic mannosides / Melonney Patrick. Masters thesis, University of Malaya.

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Abstract

Glycolipid consists of sugar head group bonded to hydrocarbon chain through a glycosidic link. It plays important biological functions in nature, such as endo- and exocytosis, apoptosis, and molecular recognition at the cell surface specific to the cell type. Synthetic glycolipid which closely mimic natural glycolipids are highly in demand as membrane model systems and it can be synthesized either chemically or enzymatically. Herein, five series of branched chain glycolipids with mannose as the head group and different total chain length from C8 to C24 carbons have been prepared. The effect of chain branching on their liquid crystalline phases were investigated by optical polarizing microscopy (OPM), differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). A comparison of these showed that they have different mesomorphism as the chain length increases. In the dry state, the shorter chain compounds, α-Man-OC6C2 and α-Man-OC8C4 exhibit lamellar phase. The phase for middle chain mannoside, α-Man-OC10C6 could not be assigned conclusively at the room temperature, but this metastable phase transformed to lamellar above 37°C. Meanwhile, the longer chain compounds, α-Man-OC12C8 and α-Man-OC14C10 form inverse bicontinuous cubic phase of space group Ia3d and inverse hexagonal phase, respectively. The lyotropic phase behaviour was determined using a contact penetration technique. In α-Man-OC6C2, the water rich side of the sample turned to an isotropic micellar solution. The α-Man-OC8C4 remains as lamellar phase upon hydration. An inverse bicontinuous cubic phase of space group Pn3m is observed in the fully hydrated α-Man-OC10C6. Both α-Man-OC12C8 and α-Man-OC14C10 give inverse hexagonal phase in excess water. The iv formation of lamellar and non-lamellar phases by these compounds makes them ideal candidates for a variety of applications such as controlled release drug-carrier.

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