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

我们的最终目标是通过外部刺激（如电场或紫外线）来控制立方（Cub）和近晶C （SmC）中间相之间的转变。本项目选择的体系为1,2-二（4′-n-烷氧苯甲酰）肼（BABHs），具有不同的烷基链长（n，其中n为烷基链上的碳原子数，本研究中从4到22不等）。为了建立一个新的紫外响应分子体系，制备了BABH与4,4′-n-烷氧偶氮苯（AZO）二元混合物，并研究了它们的相行为和对紫外光的响应行为。得到了以下结果：1。首先，我们主要通过x射线衍射和红外测量来研究宿主化合物BABHs的微观结构。通过对n-温度图的调查，发现了两种具有ia3 （n = 5- 13,15 -22）和Im3m （n = 13-16）对称性的Cub相；在一定温度下，i3d -Im3m - i3d的相序随着n的增大而增大。当温度变化时，n = 13、15和16的成员呈现出cubb - cub相变。通过对短链和长链成员形成的两种ia3 - cub相的填充研究，我们得出结论：BABH体系提供了从低分子质量液晶到微偏析的广泛自组织过程，并在两种机制的交界点实现了Im3m-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Ia3d-Cub和SmC相之间的可逆光切换。

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.