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

•The phase behaviour of mixed monoglycerides in water system has been investigated.•The phase diagram shows three bicontinuous cubic phases.•The swelling of head group progressed up to 50% of water.

Lyotropic liquid crystalline phases are formed over a limited range of surfactant concentrations and temperatures as represented by regions on the phase diagram. Acknowledgement of the surfactant phase diagram is a major step in developing any industrial application. In this work; we have examined the phase behaviour of mixed saturated and unsaturated monoglycerides 1:1 (by weight) together with water. The main technique employed was X-ray diffraction, supplemented by optical microscopy and differential scanning calorimetry (DSC). The phase diagram which is a novel finding shows six phases for GMS/GMO mixture without water: α-gel (Lβ) phase, new α-gel (Lβ1) structure, β1 crystal phase, sub-α phase, β2-crystal, as well as an isotropic, L2, phase. In the presence of water five additional phases are formed, fluid lamellar phase, three bicontinous cubic phases, Ia3d, Pn3m and Im3m with increasing the water content, and on further heating all bicontinous cubic phase convert to a hexagonal phase. Our results show that the maximum swelling capacity of the mixture of monoglycerides in water is obtained at 50% (w/w) water content, and there are important differences in the phase behaviour between mixed saturated and unsaturated monoglycerides with and without water.

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