溶致液晶相的凝胶化-液晶有序与物理凝胶形成之间的相互作用。,Langmuir

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溶致液晶相的凝胶化-液晶有序与物理凝胶形成之间的相互作用。
Langmuir ( IF 3.7 ) Pub Date : 2019-10-31 , DOI: 10.1021/acs.langmuir.9b02621
Sonja Dieterich ₁ , Thomas Sottmann ₁ , Frank Giesselmann ₁

Affiliation

我们介绍了胶凝溶致液晶（LLCs）的系统研究。这类新的软材料将LLCs的各向异性与物理凝胶的机械稳定性结合在一起。研究的LLC系统由十二烷基硫酸钠作为表面活性剂，正癸醇作为辅助表面活性剂以及水作为溶剂组成。在室温下，根据组成，形成了四个液晶相（层状Lα，向列Nd和Nc和六角形H1）。我们成功地用低分子量有机胶凝剂12-羟基十八碳二烯酸（12-HOA）胶溶了层状相。所获得的凝胶状层状相显示出光学双折射，弹性响应，并且没有宏观流动。但是，我们无法获得具有六边形或向列结构的凝胶。这些发现可以被双重解释。当使六方相胶凝时，破坏了长距离的六边形顺序，并形成了各向同性的凝胶。原因可能是凝胶纤维网络与圆柱状胶束在六方相中的二维远距离平移顺序不兼容。否则，在胶凝过程中，溶致向列相被转变为具有层状结构的各向异性凝胶。显然，将胶凝剂12-HOA添加到溶致体系中会显着拓宽层状结构，因为将表面活性12-HOA胶凝剂分子整合到向列胶束中可以使胶束曲率变平。我们进一步研究了成功的胶凝Lα相，以检查凝胶网络和其余单体胶凝剂对胶凝层状相的结构和性能的影响。

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Gelation of Lyotropic Liquid-Crystal Phases-The Interplay between Liquid Crystalline Order and Physical Gel Formation.

We present a systematical investigation of gelled lyotropic liquid crystals (LLCs). This new class of soft materials combines the anisotropy of LLCs with the mechanical stability of a physical gel. The studied LLC system consists of sodium dodecyl sulfate as a surfactant, n-decanol as a cosurfactant, and water as a solvent. At room temperature, four liquid crystalline phases (lamellar Lα, nematic Nd and Nc, and hexagonal H1) are formed depending on the composition. We were successful in gelling the lyotropic lamellar phase with the low-molecular-weight organogelator 12-hydroxyoctadecanoic acid (12-HOA). The obtained gelled lamellar phase shows optical birefringence, elastic response, and no macroscopic flow. However, we were not able to obtain gels with hexagonal or nematic structure. These findings can be explained twofold. When gelling the hexagonal phase, the long-range hexagonal order was destroyed and an isotropic gel was formed. The reason might be the incompatibility between the gel fiber network and the two-dimensional long-range translational order of the cylindrical micelles in the hexagonal phase. Otherwise, the lyotropic nematic phase was transformed into an anisotropic gel with the lamellar structure during gelation. Evidently, the addition of the gelator 12-HOA to the lyotropic system considerably widens the lamellar regime because the integration of the surface-active 12-HOA gelator molecules into the nematic micelles flattens out the micelle curvature. We further investigated the successfully gelated Lα phase to examine the impacts of the gel network and the remaining monomeric gelator on both the structure and properties of the gelled lamellar phase. Small-angle X-ray scattering results showed an arrested lamellar layer spacing in the gelled state, which indicates a higher translational order for the gelled lamellar phases in comparison with their gelator-free counterparts.

更新日期：2019-11-01

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