Aging and Metastability of Monoglycerides in Hydrophobic Solutions

Abstract

The aging of aggregated structures of monoglycerides in hydrophobic medium is described by a set of different techniques. Polarized microscopy was used to study the mesomorphic behavior as a function of time. Differential scanning calorimetry was utilized to quantitatively monitor changes in the latent heat in different phase transformations that take place in the aging system. Infrared spectroscopy was applied to detect the formation of hydrogen bonding between surfactants. The X-ray diffraction patterns fingerprinted the molecular arrangement in different emerging phases. Infra-red spectroscopy was used to monitor the state of hydrogen bonding in the system. We conclude that in both inverted-lamellar and sub-alpha crystalline phases, monoglyceride molecules inevitably lose their emulsified ability in the hydrophobic solutions through the gradual change in hydrogen bonding patterns. On aging, the formation of intermolecular hydrogen bonding between glycerol groups causes the segregation of chiral (D and L) isomers within the bilayers. Therefore all structures were eventually forced to reorder into the betacrystalline state, distinguishing between the D and L layers. Accordingly, the highly ordered packing of aged structures weakened the emulsifying ability and finally leaded the collapse of the percolating gel network.

Shear Nanostructuring of Monoglyceride Organogels

“…These peaks are due to the in-plane ordering of monoglyceride aliphatic chains into the β phase, as suggested by Chen et al 11 and Chen and Terentjev. 12 Shear-crystallized samples did not show different XRD patterns (data not shown) indicating that this processing condition did not affect either inter-plane spacing or the subcell packing of the monoglyceride crystals.…”

Novel polymer-free iridescent lamellar hydrogel for two-dimensional confined growth of ultrathin gold membranes

“…There is only one peak at 3,404 cm À 1 in both of the two spectra. This peak corresponds to the hydrogen bonding between HGM and water, and no peaks corresponding to the hydrogen bonding formed by intermolecular HGM are observed 23 . It reveals that HGM prefers to form hydrogen bond with water rather than with HGM molecules.…”

“…Here we consider a homogenous Au membrane with thickness of h, illuminated by normally incident light with the wavelength l. By applying the boundary conditions at each boundary of the membrane, the reflection and transmission coefficients r and t, respectively, can be expressed as r¼ r 12 þ r 23 the reflectivity and transmissivity are given by <¼ j r j 2 and I¼ n3 n1 j t j 2 (ref. 34).…”

The phase behaviour of mixed saturated and unsaturated monoglycerides in water system

“…The long chain saturated monoglycerides form a highly hydrated lamellar phase above a certain critical temperature [12]. When the lamellar phase is cooled the α-gel phase is formed, which eventually transforms to an anhydrous crystalline phase (the "coagel") [13,14] The head groups in the lamellar phase are more hydrated than in the α-gel phase. This reduced hydration is probably attributable to the ordered alkyl chain array of gel phase, which forces the head groups closer together than in the lamellar phase.…”