Headgroup-Dependent Thermotropic and Lyotropic Phase Behavior and Emulsifying Behavior of Guerbet Branched-Chain Glycolipids.

Guerbet alcohols have been used to synthesize glycolipids (GLs) that mimic the properties of natural GLs. This study examines how headgroup size influences thermotropic and lyotropic behavior, as well as emulsion stability. Under dry condition, 2-dodecylhexadecyl-β-d-xyloside (βXylC16C12) and 2-dodecylhexadecyl-β-d-glucoside (βGlcC16C12) formed an inverse hexagonal phase (H2), while 2-dodecylhexadecyl-β-d-maltoside (βMalC16C12) exhibited polymorphism where the GL displays a series of phases from lamellar (Lα) to nonlamellar (inverse bicontinuous cubic (V2) and H2) upon heating. Dielectric spectroscopy probed the dynamics of these phase assignments, revealing distinct relaxation signatures that track the Lα, V2, and H2 transitions in βMalC16C12. Vogel-Fulcher-Tammann analysis confirmed that the larger headgroup increases molecular cooperativity and the energy barrier for primary α-relaxations. In excess water condition, βXylC16C12 and βGlcC16C12 remained as hydrated solids, while βMalC16C12 formed a Lα phase. Emulsification tests in various oils showed that βGlcC16C12 provided the highest stability over 5 days. These findings demonstrate the significant influence of headgroup structure on packing, phase transitions, and emulsification, guiding the design of GLs as biodegradable alternatives in pharmaceutical, food, and cosmetic formulations.