Self-assembly, thermotropic and lyotropic behaviour of synthetic branched-chain alkylmaltosides / Nur Asmak Nabila Saari
Maltose sugar (normally used widely in candy industry and intravenous injection) in this study is used as the hydrophilic headgroup attached to the Guerbet chain. The effect of chain branching on glycolipid thermotropic and lyotropic phases was investigated for a series of synthetic β-D-maltoside...
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| Format: | Thesis |
| Published: |
2018
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| Online Access: | http://studentsrepo.um.edu.my/9525/1/Nur_Asmak_Nabila_Saari.pdf http://studentsrepo.um.edu.my/9525/9/asmak.pdf http://studentsrepo.um.edu.my/9525/ |
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| Summary: | Maltose sugar (normally used widely in candy industry and intravenous injection) in
this study is used as the hydrophilic headgroup attached to the Guerbet chain. The effect
of chain branching on glycolipid thermotropic and lyotropic phases was investigated for
a series of synthetic β-D-maltosides derived from Guerbet alcohols, whose total
hydrocarbon chain length ranged from C8 to C24. Synthesis and characterisation of various
branched-chain glycolipids have been attempted as these are suitable models for further
study on the structure and mechanism of cell membrane. Since natural glycolipids
compound have limited availability and require extensive syntheses, similar compounds
that can mimic the property of natural materials were synthesised for applications in the
field of biophysics and biotechnology. The branched-chain glycolipids have been
reported to produce the inverse liquid crystal structures inducing various changes in the
physicochemical properties of the disaccharide-based glycolipids self-assembly. The
compounds were synthesised to a high purity and their liquid crystalline phases were
characterised using differential scanning calorimetry (DSC), optical polarising
microscopy (OPM), and small-angle X-ray scattering (SAXS). Thermal investigations of
all anhydrous Guerbet maltosides showed that they do not form solid crystals but undergo
a glass transition upon temperature change in the range of 35 to 53 °C. The glassy
crystalline structure turns into the liquid crystalline structure upon heating or addition of
water. In thermotropic studies, the lamellar phase formation is prominent in shorter chain
length analogues while the longer chain compounds exhibit more frustrated form of
self-assembly in the formation of metastable state, polymorphism and inverse
bicontinuous cubic structure (Ia3d) as the synthesised maltosides possess two opposing
features from the headgroup (energetic) and the chain branching (entropic) which are equally dominant, resulting in the self-assembly to become frustrated and compromised
to give a particular thermotropic polymorphism. The clearing temperatures of these
branched-chain maltosides are in the range of 138 to 233 °C. The high clearing
temperatures are due to the extensive hydrogen bond network in the head group region.
Lyotropic studies show that the phase formation is dominated by lamellar phase for the
longer chain compounds. Normal micellar solution was also observed in the shortest chain
length maltosides due to the enlargement in hydrated maltose headgroups as observed
from the SAXS investigations. |
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