Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str.2, 06120, Halle, Germany.
Department of Engineering Materials, University of Sheffield, Robert Hadfield Building Mappin Street, Sheffield, S1 3JD, UK.
Chemistry. 2018 Oct 26;24(60):16072-16084. doi: 10.1002/chem.201802050. Epub 2018 Oct 9.
The dimensionality of self-assembled nanostructures plays an essential role for their properties and applications. Herein, an understanding of the transition from weakly to strongly coupled layers in soft matter systems is provided involving in-plane organized π-conjugated rods. For this purpose, bolaamphiphilic triblock molecules consisting of a rigid biphenyl core, polar glycerol groups at the ends, and a branched (swallow-tail) or linear alkyl or semiperfluoroalkyl chain in lateral position have been synthesized and investigated. Besides weakly coupled lamellar isotropic (Lam ), lamellar nematic (Lam ) and sliding lamellar smectic phases (Lam ), a sequence of three distinct types of strongly coupled (correlated) lamellar smectic phases with either centered (c2mm) or non-centered rectangular (p2mm) lattice and an intermediate oblique lattices (p2) were observed depending on chain length, chain branching and degree of chain fluorination. This new sequence is explained by the strengthening of the layer coupling and the competition between energetic packing constraints and the entropic contribution of either longitudinal or tangential fluctuations. This example of directed side chain engineering of small generic model compounds provides general clues for morphological design of two-dimensional and three-dimensionally coupled lamellar systems involving larger π-conjugated molecular rods and molecular or supramolecular polymers, being of actual interest in organic electronics and nanotechnology.
自组装纳米结构的维度对于它们的性质和应用起着至关重要的作用。本文提供了对软物质体系中弱耦合层到强耦合层转变的理解，涉及面内有序的π共轭棒。为此，合成并研究了由刚性联苯核、末端极性甘油基团以及侧链支化（燕尾形）或线性烷基或半氟烷基链组成的两亲性三嵌段分子。除了弱耦合层状各向同性（Lam）、层状向列相（Lam）和滑动层状近晶相（Lam）之外，还观察到了三种不同类型的强耦合（相关）层状近晶相的序列，其晶格分别为中心（c2mm）或非中心矩形（p2mm）以及中间斜晶格（p2），这取决于链长、链支化和链氟化程度。这种新序列可以通过层间耦合的增强以及能量堆积约束与纵向或切向涨落的熵贡献之间的竞争来解释。这种对小通用模型化合物的定向侧链工程的示例为涉及更大的π共轭分子棒以及分子或超分子聚合物的二维和三维耦合层状体系的形态设计提供了一般性线索，在有机电子学和纳米技术中具有实际意义。
