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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Self-assembled structures formed by a wedge-shaped molecule in 2D and 3D: the role of flexible side chains and polar head groups
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Self-assembled structures formed by a wedge-shaped molecule in 2D and 3D: the role of flexible side chains and polar head groups

机译：由楔形分子在2D和3D中形成的自组装结构：柔性侧链和极性头部基团的作用

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摘要

A wedge-shaped amphiphilic molecule, 3,4,5-tridodecyloxycinnamic acid, was used as a model system to explore the role of different constitutive elements of the chemical structure in the formation of 2D and 3D self-assemblies. The polar heads forming cyclic hydrogen-bonded dimers determine the two largest unit cell parameters, which depend only slightly on the dimensionality of the system (i.e. 2D versus 3D) and on the sample thermal history. By contrast, the structure of the alkyl side chains is very sensitive to the phase transformations, and is likely to be responsible for the rich polymorphic behaviour of the studied compound. Thus, in the monotropic SmC phase, the alkyl chains form a liquid-crystalline sub-lattice with hexagonal symmetry that can further crystallize either in a triclinic sub-cell (metastable crystalline phase) or in an orthorhombic sub-cell (stable crystalline phase). In 2D, at the interface with the graphite surface the molecular orientation is guided by the epitaxy. Although the largest lattice parameters are close to those in the bulk, the alkyl chains adopt a particular alternating orientation. In one molecule of the dimer, two alkyl chains have their molecular planes parallel to the substrate while the third chain is perpendicular to it, and the other way around for the other molecule of the dimer. To our knowledge, such alternating orientation of the alkyl chains in the monolayer is reported for the first time.
机译：使用楔形两亲分子3,4,5-三十二烷氧基肉桂酸作为模型系统，研究化学结构的不同组成元素在2D和3D自组装形成中的作用。形成环状氢键二聚体的极性头决定了两个最大的晶胞参数，这些参数仅略微取决于系统的尺寸（即2D与3D）和样品的热历史。相比之下，烷基侧链的结构对相变非常敏感，并且可能是所研究化合物丰富的多态行为的原因。因此，在单向SmC相中，烷基链形成具有六边形对称性的液晶子晶格，该晶格可以在三斜晶系亚晶格（可置换晶相）或正交晶系亚晶格（稳定晶相）中进一步结晶。 。在2D中，在与石墨表面的界面处，分子取向由外延引导。尽管最大的晶格参数接近于本体中的那些，但是烷基链采用特定的交替取向。在二聚体的一个分子中，两个烷基链的分子平面与底物平行，而第三条链与底物垂直，而另一侧围绕二聚体的另一个分子。据我们所知，首次报道了单层中烷基链的这种交替取向。

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