Phase Behavior of Binary Mixture System of Unsaturated Fatty Acids

采用高压差热分析技术，研究了油酸（OA；顺-9-十八烯酸）/棕榈油酸（POA；顺-9-十六烯酸）混合物在高压下的相行为。该混合物中的组分具有相同的DELTA链（双键和羧基之间的链段）长度，而omega链（双键和亚甲基端基之间的脂肪链段）长度相差2个碳。随着压力的增大，固液边界温度急剧向高温方向移动。另一方面，无论压力如何，相边界的形状几乎保持不变。还研究了POA/天冬氨酸（APA；顺-11-十八烯酸）的混合物。虽然POA/APA的混相与OA/POA的混相有很大的不同，但这两种混合物的压力响应几乎相同。这意味着这些混合物的固相特性即使在升高的压力下（至少高达200mpa）也能保持。通过熔点、熔点焓变和熔点的压力依赖关系，计算了OA/POA混合物中形成的分子络合物熔点的体积变化。得到了合理的数值。这可能有助于讨论这种分子化合物的结构，因为它的结构现在是未知的。

The phase behavior of oleic acid (OA ; cis-9 octadecenoic acid) /palmitoleic acid (POA ; cis-9-hexadecenoic acid) mixture under pressure was examined by using high pressure differential thermal analysis technique up to 200 MPa. The components in this mixture have the same DELTA chain (chain segment between double bond and carboxyl group) length, while the omega chain (aliphatic chain segment between double bond and methylene end group) length differs by 2 carbons. The temperature of solid-liquid phase boundary shift drastically toward high temperature as the pressure increases. On the other hand, the shape of the phase boundary remained almost unchanged regardless of the pressure.The mixture of POA/asclepic acid (APA ; cis-11-octadecenoic acid) is also examined. Although the miscibility of POA/APA is quite different from OA/POA,the pressure response of these mixtures are almost the same. That means that the characteristic features in solid phase of these mixtures are retained even under elevated pressure, at least up to 200 MPa.The volume change on the melting of molecular complex formed in the OA/POA mixture was calculated by the pressure dependence of the melting point, enthalpy change of melting, and pelting point. The reasonable value was obtained. This might be helpful to discuss the structure of this molecular compound, because the structure is unknown right now.