Control of Dimensionality in Packing Structures Formed by Cubic Mesogens and Development of a New Molecular System

我们的最终目标是控制立方（Cub）和近晶C（SmC）介晶相之间的转变，通过外部刺激，如电场或紫外光。本项目中选择的体系是具有不同烷基链长度（n，其中n是烷基链中的碳原子数，在本研究中从4变化到22）的1，2-双（4 '-n-烷氧基苯甲酰基）肼（BABH）。为了构建一种新型的紫外光响应分子体系，制备了BABH与4，4 '-n-烷氧基偶氮苯（AZO）的二元混合物，研究了它们的相行为和紫外光响应行为。获得了以下结果：1.首先，我们主要通过X射线衍射和红外测量研究了主体化合物BABH的微观结构。测量了n-温度图，发现有Ia 3d（n = 5-13，15-22）和Im 3 m（n = 13-16）两种对称性的Cub相，在一定温度下，随着n的增大，出现Ia 3d-Im 3 m-Ia 3d的相序。当温度变化时，n = 13，15和16的成员呈现Cub-to-Cub相变.通过对由较短和较长链成员形成的两个Ia 3d-Cub相的堆积研究，我们得出结论：BABH体系提供了从低分子量液晶区到微观偏析区的广泛的自组织过程，并且在两个区域之间的边界处实现了Im 3 m-Cub相的形成.最后，对于具有优化组成的BABH-AZO混合物，我们成功地观察到Ia 3d-Cub和SmC相之间的可逆光开关。

Our ultimate goal is to control the transition between cubic (Cub) and smectic C (SmC) mesophases by external stimuli such as electric field or UV light. The system selected in this project is 1,2-bis (4'-n-alkoxybenzoyl) hydrazines (BABHs) with various alkyl chain lengths (n, where n is the number of carbon atoms in the alkyl chain and in this investigation varies from 4 to 22). To build a new molecular system responsive to UV light, binary mixtures of the BABH with 4,4'-n-alkoxyazobenzenes (AZO) were prepared and their phase behavior and response behavior to UV light irradiation were investigated. The following results were obtained:1. First, we investigated the microstructure of the host compounds BABHs mainly by X-ray diffraction and infrared measurements. The n-temperature diagram was surveyed and two types of Cub phases with Ia3d (n = 5-13, 15-22) and Im3m (n = 13-16) symmetries were found; at a given temperature is seen the phase sequence of Ia3d -Im3m -Ia3d on going to larger n. The members with n = 13, 15, and 16 exhibit a Cub-to-Cub phase transition when temperature is varied.2. From the packing study for the two Ia3d-Cub phases formed by shorter and longer chain members, we conclude that the BABH system provides a broad range of self-organization process from the low molecular mass liquid crystalline regime to the micro-segregation regime, and at the borderline between the two regimes the formation of the Im3m-Cub phase is realized.3. Finally, for a BABH-AZO mixture with an optimized composition, we successfully observed a reversible photo-switching between the Ia3d-Cub and SmC phases.