Mesophase characterization of some long chain vicinal multihydroxy amphiphiles [1,2]

Abstract

The mesophase characterization of three stereoisomeric multihydroxy compounds, the 1,2(S), 3(R),4(R)-, 1,2(R), 3(S), 4(R)-, and 1,2(S), 3(S),4(R)-icosanetetrols, as well as of an octadecafuranose derivative has been carried out by means of polarizing microscopy, X-ray diffraction etc. The four multiols with their very long flexible alkyl chains are mono-thermomesomorphic; their single mesophases are miscible with each other, with a typical carbohydrate derivative, and are characterized by X-ray diffraction having a layer structure without order in it. The phase transition data of the three icosanetetrols are strongly dependent on their stereochemistry. The measurements of the refractive indices of one of the tetrols show a typical behaviour known for S, phases or for lamellar phases, i.e. the sign of the birefringence is positive.

Synthesis and Self-Assembly of Donor−Spacer−Acceptor Molecules. Liquid Crystals Formed by Single-Component “Complexes” via Intermolecular Hydrogen-Bonding Interaction

“…For example, carboxylic acids including 4-alkoxybenzoic acids and trans - p -methoxy- and ethoxycinnamic acids dimerize through intermolecular hydrogen bonds and thus induce liquid crystallinity. Other examples on liquid crystals developed by identical amphiphilic species, such as carbohydrates, , polyols, , etc., were also reported. Kato and Fréchet 4 first exploited two different and independent components to generate liquid crystals through intermolecular hetero- hydrogen-bonding interaction, and this concept in turn resulted in numerous findings of such supramolecular liquid crystals. − On the basis of the above strategy, Griffin et al − studied extensively main-chain linear hydrogen-bonded liquid crystals generated by bipyridyl derivatives and aromatic dicarboxylic acids.…”

Stereochemistry-dependent thermotropic liquid crystalline phases of monosaccharide-based amphiphiles

“… 51 Only Sm phases have been observed for mono alkylated polyol derivatives. 75 Hexagonal phases have been detected for carbohydrate derivatives possessing dual carbon tails which lead to disk-like multimer formation and lack of Sm phase formation. 31 With singular and long enough hydrocarbon tail to obtain the larger volume fraction (and free volume) from the polyol, t -Man*-SC14 forms a hexagonal cylinder transition structure at 170 °C (hydrogen bonds are highly dynamic at this high enough temperature).…”

Unveiling the hydrogen bonding network in liquid crystalline natural-based glycosides containing polymeric complexes: Experimental and theoretical assessment

“…More specifically, the different hydroxyl groups can form multiple hydrogen bonds between glycosides, resulting in microphase separation between polar and non-polar regions, and ultimately favouring smectic behaviour [23][24][25][26][27][28][29] . We note, however, that the exhibition of liquid J o u r n a l P r e -p r o o f crystalline phases is not based on the formation of new "rod-like" or "disc-like" moieties by hydrogen-bonding, but instead on segregation due to the amphiphilic character of the glycosides, including hydrogen-bonding between the sugar heads.…”