A reevaluation of the epimeric and anomeric relationship of glucosides and galactosides in thermotropic liquid crystal self-assemblies

Anomers and epimers α- and β-gluco and -galactosides are expected to behave differently. However, recent results on a series of Guerbet glycosides have indicated similar liquid crystal clearing temperatures for pure β-glucosides and the corresponding α-galactosides. This observation has led to speculation on similarities in the self-assembly interactions between the two systems, attributed to the trans-configuration of the 4-OH group and the hydrophobic aglycon. Previous simulations on related bilayers systems support this hypothesis, by relating this clearing transition temperature to intralayer (sugar–sugar) hydrogen bonding. In order to confirm the hypothesis, the comparison was expanded to include the cis-configurated pair, that is, α-gluco/β-galactoside. A set of α-configurated Guerbet glucosides as well as octyl α-galactoside were prepared and their thermotropic phase behavior studied. The data obtained enabled a complete comparison of the isomers of interest. While the results in general are in line with a pairing of the stereo-isomers according to the indicated cis/trans-configuration, differences within the pairs can be explained based on the direction of hydrogen bonds from a simple modeling study.

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► Observed trend of clearing temperatures for gluco-/galactoside is TβGal > TαGlc > TβGlc ∼ TαGal.
► Trend suggests regrouping of gluco-/galactosides to cis/trans epimeric–anomeric pairs.
► Different lipid tilt angles in hydrophobic region for single and double chain change this ranking.
► Intra-layer hydrogen bonds and sugar cooperativity influence liquid crystal phase stability.