Phase behavior of binary mixtures of cis-monounsaturated fatty acids with different ω-chain length

Abstract

Phase diagrams of binary mixtures of oleic acid (OA)/palmitoleic acid (POA) and OA/myristoleic acid (MOA) were constructed by differential scanning calorimetry to examine the mixing behavior of cis-monounsaturated fatty acids with different ω-chain length in polymorphic phases. The phase diagram for OA/POA mixtures demonstrates that the molecular compounds of OA 3POA 2 and of OA 1POA 2 are formed in α phase and in γ phase, respectively. The compound forms solid solutions with OA and also with POA in the α phase, whereas both OA 1POA 2/OA and OA 1POA 2/POA in γ phase are perfectly immiscible. As for OA/MOA mixtures, the compound OA 2MOA 3 is formed from MOA and the α polymorph of OA. The solid solution is formed between the compound and MOA, while the miscibility between the compound and OA is much poorer. The present study reveals that the conformational state of the ω-chain, i.e. ordered (γ-form) or disordered (α-form), strongly affects the phase behavior of binary mixtures of cis-monounsaturated fatty acids.