Vaupotič Nataša, Salamończyk Mirosław, Matraszek Joanna, Vogrin Martin, Pociecha Damian, Gorecka Ewa
Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška 160, 2000 Maribor, Slovenia.
Phys Chem Chem Phys. 2020 Jun 14;22(22):12814-12820. doi: 10.1039/d0cp01579b. Epub 2020 May 29.
We have studied properties of novel thermotropic mesogenic materials that exhibit both an achiral double gyroid (Ia3[combining macron]d symmetry) and chiral cubic phase (previously assigned the Im3[combining macron]m symmetry). We argue that in the chiral cubic phase molecules form micelles and channels arranged into continuously interconnected hexagons. From the X-ray diffraction experiment supported by modelling, exact positions of hexagons and their connections were deduced and showed to be embedded on a WP (degenerated Neovius) minimal primitive surface. The elastic energy of such a structure is close to the one of the double gyroid phase, which is in agreement with a very low enthalpy change observed at the phase transition. We also argue that the chirality of the phase is related to the lack of mirror symmetry of non-flat hexagons accompanied by an alternating inclination of molecules in the neighbouring segments of hexagon; the chirality of individual hexagon is amplified on the whole hexagon network by steric effects.
我们研究了新型热致液晶材料的性质，这些材料既呈现出非手性双螺旋面（Ia3̅d对称性）又呈现出手性立方相（先前被指定为Im3̅m对称性）。我们认为在手性立方相中，分子形成排列成连续相互连接六边形的胶束和通道。通过建模支持的X射线衍射实验，推导出六边形及其连接的精确位置，并表明它们嵌入在WP（退化的Neovius）最小原胞表面上。这种结构的弹性能量接近于双螺旋面的弹性能量，这与在相变时观察到的非常低的焓变一致。我们还认为，该相的手性与非平面六边形缺乏镜面对称性有关，同时六边形相邻段中分子存在交替倾斜；单个六边形的手性通过空间效应在整个六边形网络上被放大。
