PHASE-BEHAVIOR OF BINARY-MIXTURES OF CIS-MONOUNSATURATED FATTY-ACIDS WITH DIFFERENT OMEGA-CHAIN LENGTH

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 omega-chain length in polymorphic phases. The phase diagram for OA/POA mixtures demonstrates that the molecular compounds of OA3POA2 and of OA1POA2 are formed in alpha phase and in gamma phase respectively. The compound forms solid solutions with OA and also with POA in the alpha phase, whereas both OA1POA2/OA and OA1POA2/POA in gamma phase are Perfectly immiscible. As for OA/MOA mixtures, the compound OA2MOA3 is formed from MOA and the alpha 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 omega-chain, i.e. ordered (gamma-form) or disordered (alpha-form), strongly affects the phase behavior of binary mixtures of cis-monounsaturated fatty acids.