Abstract:

Alkyl α-D-glucopyranosides were synthesized with D-glucose as the raw material by three reactions involving acetylation, SnCl₄ catalyzing glycosylation with the aliphatic alcohols and deacetylation. The structures of alkyl α-D-glucopyranosides, their surface properties and thermotropic liquid crystalline properties were determined through NMR, surface tensiometer, polarization microscope and so on. The results show that alkyl α-D-glucopyranosides possess foaming and emulsifying power as their hydrophobic alkyl chain length n=6~9, wherein n-nonyl α-D-glucopyranoside has rather superior foaming and emulsifying power. The values of the surface tension(γ_CMC) and the critical micelle concentration(CMC) of the alkyl glycosides(n=6~9) are very low, their saturated adsorption capacity(Γ_max) decreases with increasing alkyl chain length, and their saturation adsorption area(A_min) increases with the increase of alkyl chain lengths. The standard free energy of micellization(ΔG_mic) and standard free energy of adsorption(ΔG_ads) for alkyl glycosides(n=6~9) are all less than zero, and the values of ΔG_mic and ΔG_ads are more negative with the increase of the alkyl chain length. The n-octyl α-D-glucopyranoside has the best surface activity. Furthermore, the alkyl glucosides(n=4~9) does not have any skin irritation. Finally, all of alkyl α-D-glucopyranosides exhibit thermotropic liquid crystalline behavior, the temperature range of the thermotropic liquid crystalline phase becomes broader, and the stability of the thermotropic liquid crystalline phase becomes stronger with the increase of alkyl chain length.

Key words: D-glucose, alkyl α-D-glucopyranoside, SnCl₄, surface performance, thermotropic liquid crystallline