Columnar mesophases constructed by hierarchical self-organization of rod-like diacetylene molecules
作者:Tomoyo Shimogaki、Satoshi Dei、Kazuchika Ohta、Akikazu Matsumoto
DOI:10.1039/c1jm10817d
日期:——
We report a new class of liquid crystalline system exhibiting columnar mesophases, which are constructed by the hierarchical supramolecular self-organization of a rod-like diacetylene derivative as the primary building block. A series of 1,3-alkadiynyl-4-benzoic acids (mmDA) with different alkyl chain lengths (m = 8–16) were synthesized and their mesophase properties were investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction under temperature control. The mmDA exhibited three types of mesophases, i.e., a discotic lamellar phase, DL, and two columnar rectangular phases, Colrd and Colro, with disordered and ordered stacking structures of the mesogens in a column, respectively, depending on the length of the alkyl substituent and temperature. We have revealed that the columnar mesophase structures are constructed with the rod-like mmDA molecules as the starting building blocks by hierarchical self-organization. The hydrogen-bonded dimers of the carboxylic acid with a rigid framework are assembled to provide a disc-like mesogen unit, which consists of a π-stacked core-part and peripheral alkyl-chains. The discotic supramolecular mesogens further stack in ordered and disordered columnar structures, producing the Colro and Colrd mesophases, or in the layer DL mesophase. This is a rare example for the discotic mesophases using the rod-like diacetylenes with a non-branched molecular structure.
我们报告了一类新型的具有柱状中间相的液晶系统,该系统是由棒状丁二炔衍生物的分层超分子自组织作为主要构建单元构建的。合成了一系列具有不同烷基链长度 (m = 8–16) 的 1,3-烷二炔基-4-苯甲酸 (mmDA),并通过差示扫描量热法、偏光光学显微镜和 X 射线衍射研究了它们的中间相性质在温度控制下。 mmDA表现出三种类型的中间相,即盘状层状相DL和两个柱状矩形相Colrd和Colro,根据烷基取代基的长度,分别在柱中具有无序和有序的介晶堆叠结构和温度。我们揭示了柱状中间相结构是通过分层自组织以棒状mmDA分子作为起始构建块构建的。具有刚性骨架的羧酸的氢键二聚体组装成盘状介晶单元,该单元由π堆叠的核心部分和外围烷基链组成。盘状超分子介晶进一步堆叠成有序和无序的柱状结构,产生 Colro 和 Colrd 中间相,或形成层 DL 中间相。这是使用具有非支化分子结构的棒状丁二炔的盘状中间相的罕见例子。