Mesogenic sugars. From aldoses to liquid crystals and surfactants

Abstract

Amphiphilic sugar derivatives, formed by condensation of functionalized aliphatic chains with aldoses, form liquid crystals, in most cases smectic. A puzzling observation was the failure of the S,S-acetals of 6-deoxy sugars, L-rhamnose and D-fucose, to form such phases. A satisfactory model to explain this behavior involves-in most cases-the formation of columns, which are destabilized with the deoxy sugars in which the apolar end methyl groups are pushed together.Despite the abundance of chiral centers in the mono-and disaccharides used the smectic phases themselves in general display no chirality. By appropriate molecular design in which the amphiphilic character was deliberately suppressed it was possible to prepare glucose derivatives that exhibit chiral nematic phases as well as impressive helical twisting powers. Simple condensation chemistry is used to produce such derivatives.The amphiphilic character can be deliberately enhanced, and this is readily achieved in double headed 'gemini' derivatives formed by condensation of glucose or lactose with a long chain diamine followed by reduction followed by acylation of the nitrogen atoms with long chain acyl anhydrides. The thermodynamics of micellization of precursors to these derivatives have been studied. The gemini derivatives themselves display remarkable properties including the formation of giant vesicles and an appreciable capacity for the solubilization of hydrocarbons.

Shape Dependence in the Formation of Condensed Phases Exhibited by Disubstituted Sucrose Esters

“…[27] Amphiphiles with sugars or cyclic and acyclic polyols as polar heads with single, apolar aliphatic chains attached to the head groups tend to display smectic phases. [3,4,[28][29][30] Thermotropic columnar mesophases with the head groups located towards the interior of the columns have also been obtained by grafting several fatty-acid chains onto the polar head, thereby increasing the volume ratio of fatty-acid chain to polar head group, leading to changes in curvature and, hence, packing constraints of the molecules. [3,[31][32][33] Columnar mesophases also have been obtained by increasing the volume of the head group relative to the aliphatic region.…”

Self‐Organizing Properties of Monosubstituted Sucrose Fatty Acid Esters: The Effects of Chain Length and Unsaturation

“…[21] Most amphiphiles, which contain sugars or cyclic and acyclic polyols as polar heads, have been found to exhibit smectic A* phases. [24][25][26] A limited number of inverted thermotropic, disordered columnar mesophases have also been obtained by grafting several fatty chains on to the polar head group, thus increasing the volume ratio of fatty chain to polar head group, thereby leading to changes in curvature. [27,28] Inverted hexagonal columnar mesophases have been obtained by increasing the volume of the head group from a single-sugar head to double-sugar head, but still with the attachment of a single aliphatic chain.…”

Manifestation of a Chiral Smectic C Phase in Diphenylbutadiene‐Cored Bolaamphiphilic Sugars

“…[15,18,19] However, the mechanism by which molecular chirality is transferred to macroscopic chirality of the LC phases still remains an intriguing subject. [15] Sugars are a naturally abundant, inexpensive class of chiral molecules, [20,21] which could be used as components for the design of chiral LCs. Since Emil Fischer and Burckhardt Helferich first reported in 1911, the double melting point of cetyl-b-D-glucoside, [22] which was later recognized as the evidence for the formation of thermotropic LCs, [23] a large number of sugar-based LCs have been synthesized and examined.…”

“…Since Emil Fischer and Burckhardt Helferich first reported in 1911, the double melting point of cetyl-b-D-glucoside, [22] which was later recognized as the evidence for the formation of thermotropic LCs, [23] a large number of sugar-based LCs have been synthesized and examined. [20,21,[23][24][25][26][27][28][29] An interesting aspect of the selforganizing behavior of amphiphilic sugars is that in spite of the abundance of chiral centers, their LC phases generally exhibit smectic, columnar or cubic phases which do not possess macroscopic chirality. [15,20,21] Similarly, absence of macroscopic chirality was also observed in the smectic phases exhibited by bolaamphiphiles consisting of oligomethylene A series of symmetrical bolaamphiphiles possessing a diphenylbutadiene core and glucopyranoside head groups linked together by oligomethylene spacers, were synthesized and their thermotropic liquid crystalline properties investigated by polarized light optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optic switching.…”

“…[20,21,[23][24][25][26][27][28][29] An interesting aspect of the selforganizing behavior of amphiphilic sugars is that in spite of the abundance of chiral centers, their LC phases generally exhibit smectic, columnar or cubic phases which do not possess macroscopic chirality. [15,20,21] Similarly, absence of macroscopic chirality was also observed in the smectic phases exhibited by bolaamphiphiles consisting of oligomethylene A series of symmetrical bolaamphiphiles possessing a diphenylbutadiene core and glucopyranoside head groups linked together by oligomethylene spacers, were synthesized and their thermotropic liquid crystalline properties investigated by polarized light optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optic switching. In spite of the presence of chiral centers, amphiphilic sugars in general do not exhibit macroscopic chirality and this phenomenon is attributed to strong hydrogen bonding between sugar head groups resulting in microphase-segregated layer like arrangements.…”