A Coupled Differential Scanning Calorimetry and X-ray Study of the Mesomorphic Phases of Monostearin and Stearic Acid in Water

Abstract

Differential scanning microcalorimetry coupled to Synchrotron small angle X-ray scattering (SAXS) was used to characterize the mesomorphic phases of monostearin ; a series of dispersions of monostearin and stearic acid (95:5 w/w) in alkaline water were prepared in the range 5-90% (w/w). Samples were subjected to both melting and cooling regimes from 45 to 81 at 2 °C/min in a Microcalix machine (an X-ray sample chamber with microcalorimetry capabilities), while X-ray spectra and the microcalorimetric trace were being collected simultaneously. Using these two techniques, two-dimensional phase diagrams of the mesomorphic phases (lyotropic and thermotropic liquid crystalline phases as well as the crystalline, hydrated gel phases) of monostearin was created, one for heating and one for cooling, and the typical X-ray diffraction pattern for each of the phases was identified. Polarized light microscopy was also used in an attempt to differentiate and identify the mesomorphic phases. Furthermore, the largest d-spacings (which includes the thickness of the water domain and the lipid bilayer) for each of the different monostearin concentrations were plotted at 73 °C during heating and when cooling, to better understand the water binding capacity of the different mesomorphic phases. This information will provide guidance for the use of these unique phases in food and pharmaceutical applications.

Structural and mechanical properties of organogels: Role of oil and gelator molecular structure

“…Thixotropy and apparent viscosity at 3 s −1 (η 3 ) for OMCT and OLCT produced with GT, GM, ST and SM for increasing concentrations of gelator (5%, 10%, 15%, 20% and 25%, w/w) (Nnot performed). structure due to the increase of gelator concentration (Zetzl, Ollivon, & Marangoni, 2009). It is interesting to note that for the highest concentration of gelator (25% w/w) the structure changes again, since the formation of a lamellar structure with a d-spacing similar to the one obtained for 5% (w/w) of gelator (Table 2) was observed.…”

Influence of Surfactant and Lipid Type on the Physicochemical Properties and Biocompatibility of Solid Lipid Nanoparticles

“…Addition of surfactant can force the stearic acid to crystallize regardless of the crystallization conditions and the nature of the solvent [ 22 ]. A cubic phase occurs in some systems with chain lengths above C14, which structure consist of two interpenetrating networks of rod-like aggregates and it has been suggested from theoretical point of view that there are two fundamentally different alternatives for cubic lipid-water structures, (i) structures with continuous regions of both water and hydrocarbon chains and (ii) structures composed of closed aggregates of “oil-in-water” or “water-in-oil’’ type, this added to the effects of surfactant could explain the formation of particles with regions showing domains with different electron-densities seen on TEM, however deeper studies should be performed to understand the formation of the presented SLNs [ 23 , 24 ].…”

Nature and dynamics of monostearin phase transitions in water: stability and the sub-α-gel phase

“…[1][2][3][4][5] Depending on temperature and age, MG-structured systems and MG crystals occur in the sub-a phase, a phase, b phase, liquid crystal lamellar phase and cubic phase depending on temperature and age. [1][2][3][4][5][6][7] The phase behavior of saturated MG crystals has been studied extensively. 3,5,[7][8][9] Crystals of glycerol monosteatate (GMS) and glycerol monopalmitate (GMP) have more than four different polymorphic forms as neat solids.…”

“…The system cannot revert back to the a-gel phase without heating above the Kra temperature and forming the lamellar phase again. 6,13,16,17 Cooling the MG-gel under shear or shearing aer cooling accelerates the a-gel to coagel phase transition and enhances the release of water. 4,18,19 The a-gel phase or the coagel phases are accessible at 10-60% (w/w) MG in water concentrations below 55 C. 6 Further heating of the MG-gel above 80 C may cause the formation of cubic phases.…”

“…6,13,16,17 Cooling the MG-gel under shear or shearing aer cooling accelerates the a-gel to coagel phase transition and enhances the release of water. 4,18,19 The a-gel phase or the coagel phases are accessible at 10-60% (w/w) MG in water concentrations below 55 C. 6 Further heating of the MG-gel above 80 C may cause the formation of cubic phases. 6,17 Only the XRD peak positions of the a-gel form and the coagel form have been identied in literature, while the diffraction peak positions of the sub-a phase had not been identied in MG-water system (Table 1).…”