胆甾醇长链脂肪酸酯类液晶相变的热力学研究

Studies on phase change thermodynamics of the liguid crystals of choleteryl long-chained aliphatic acid esters

本文用美国PE公司DSC—7型差示扫描量热法研究了胆甾醇肉豆蔻酸酯和硬脂酸酯液晶的熔融和清亮过程热力学,准确测定了相变温度和相变焓,并计算了相应的相变熵。发现胆甾醇肉豆蔻酸酯在升温和降温过程中均出现液晶相,而胆甾醇硬脂酸酯仅在降温过程中才出现液晶相,随着脂肪酸碳链的增长,清亮点下降,而清亮焓和清亮熵增大。并从液晶态的分子微观结构和链段与链段相互作用作了定性解释。

In this work, the phase change thermodynamics of cholestenyl myristate and stearate ligu-id crystals has been studied by DSC. The temperatures and the enthalpies of the phase change were obtained accurately, and the entropies were calculated according to ΔS=ΔH/T. The results show that the cholesteryl stearate melts directly to an isotropic liquid and forms mesophases on coolig, while the cholesteryl myristate forms mesophases both on heating and on cooling. the clear points decrease with the increase of the length of the alkanoate chains, while the enthalpies and entropies increase with it. this may be interpreted from the point of view of molecular microstructure and the occurring of additional ordering.