Carbohydrate liquid crystals: Synthesis and characterisation of the methyl-6-O-(n-acyl)-α-d-glucopyranosides

New insights into the transitional behaviour of methyl-6-O-(n-dodecanoyl)-α-D-glucopyranoside using variable temperature FTIR spectroscopy and X-ray diffraction

“…The synthesis of methyl-6-O-dodecanoyl-α-D-glucopyranoside, 1, and the characterisation of its thermal behaviour have been described in detail elsewhere. [16] X-ray diffraction measurements were carried out using a custom-built beamline based on a Bede Microsource system, with a Photonic Science CCD detector. The sample, in a 1.5 mm thin-wall glass capillary, was mounted in a brass holder with mylar windows in the X-ray sample chamber and heated into the isotropic phase at 74.7°C.…”

“…[11][12][13][14][15] It is clear that the successful design of new liquid crystal carbohydrates now requires an improved understanding of the empirical relationships between molecular structure and aggregation behaviour. With that aim, recently, we studied the transitional behaviour of a series of monosaccharides, the methyl-6-O-(n-acyl)-α-D-glucopyranosides, as a function of the alkyl chain length, n. [16] At sufficiently high values of n, the compounds exhibit thermotropic liquid crystallinity, specifically, a monotropic smectic A phase seen on cooling from the isotropic phase, and which can be supercooled by ca 30ºC prior to crystallising. On increasing the alkyl chain length further, liquid crystallinity is extinguished and this has been attributed to back folding of the alkyl chains which disrupts the packing of the molecules.…”

“…On increasing the alkyl chain length further, liquid crystallinity is extinguished and this has been attributed to back folding of the alkyl chains which disrupts the packing of the molecules. [16] We now investigate in greater detail the role of the different intermolecular interactions in determining the phase behaviour of the dodecyl member of this homologous series, namely, methyl-6-O-(n-dodecanoyl)-α-D-glucopyranoside, 1, shown in Scheme 1. [16] Specifically, we have characterised the phase structures shown by 1 using X-ray diffraction, and attempted to correlate these with the different chemical environments of the functional groups deduced using temperature-dependent Fourier transform infrared (FTIR) spectroscopy.…”

“…[16] Specifically, we have characterised the phase structures shown by 1 using X-ray diffraction, and attempted to correlate these with the different chemical environments of the functional groups deduced using temperature-dependent Fourier transform infrared (FTIR) spectroscopy. [17] It is important to note that the monotropic character of 1 [16] allows us to study both the crystal-isotropic and isotropic-smectic A transitions for the same compound, and to probe the differences in the change in molecular interactions occurring at these transitions which would be impossible to achieve for an enantiotropic material.…”

Hydrogen bonding and liquid crystallinity of low molar mass and polymeric mesogens containing benzoic acids: a variable temperature Fourier transform infrared spectroscopic study

“…[16][17][18] Hydrogen bonding also plays a key role in driving liquid crystalline behaviour in a diverse range of other materials including commercially important high-performance fibres, [19] protonic conductors [20,21] and liquid crystal sugars. [22][23][24][25] Supramolecular SCLCPs have attracted particular attention and these have been assembled not only using hydrogen bonding (see, for example, [7,26,27]), but also by utilising other types of non-covalent interactions such as ionic bonding [28] and quadrupolar interactions. [29] In approaching the design of a supramolecular SCLCP, it is useful first to consider the molecular architecture of a conventional SCLCP, which comprises three structural elements: a polymer backbone, a flexible spacer and a mesogenic group.…”