Kutnjak Zdravko, Cordoyiannis George, Nounesis George, Lebar Andrija, Zalar Bostjan, Zumer Slobodan
Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana, Slovenia.
J Chem Phys. 2005 Jun 8;122(22):224709. doi: 10.1063/1.1927516.
A lyotropic inverse micelle phase composed of water, thermotropic liquid-crystal octylcyanobiphenyl (8CB), and surfactant (DDAB) was studied by using high-resolution calorimetry on several mixtures with 3%, 8%, and 15% micelle concentration. Calorimetric results show strong depression of the isotropic to nematic (I-N) phase-transition temperature. Broad heat-capacity anomalies show the existence of a wide coexistence range of isotropic, nematic, and smectic-A phases, which mimics the behavior of a new nearly stable thermodynamic phase. An observation of the rather sharp almost bulklike nematic to smectic-A (N-A) transition at low-temperatures indicates that our heat capacity results are consistent with the phase separation scenario in which significant number of micelles is expelled during I-N conversion leaving almost pure nematic phase at lower temperatures. It was found that micelles get almost completely remixed on heating the mixture back to the isotropic phase.
通过使用高分辨率量热法，对由水、热致液晶辛基氰基联苯（8CB）和表面活性剂（DDAB）组成的溶致反胶束相进行了研究，研究对象为几种胶束浓度分别为3%、8%和15%的混合物。量热结果表明，各向同性向向列相（I-N）的相变温度大幅降低。宽热容量异常表明存在各向同性、向列相和近晶-A相的宽共存范围，这模拟了一种新的近稳定热力学相的行为。在低温下观察到相当尖锐的几乎类似块状的向列相到近晶-A相（N-A）转变，这表明我们的热容量结果与相分离情况一致，即在I-N转变过程中，大量胶束被排出，在较低温度下留下几乎纯的向列相。研究发现，将混合物加热回到各向同性相时，胶束几乎完全重新混合。
