Self-organization of coil-rod-coil molecular isomers with conjugated rod segments into supramolecular honeycomb and lamellar assemblies

Rod-coil molecules, consisting of flexible and rigid blocks, have a strong capacity to self-assemble into a variety of ordered nanostructures in the bulk state. In this article, we report the synthesis and the self-assembling behavior of coil-rod-coil rectilinear molecular isomers 1 and 2. These molecules consist of conjugated rod segments, which are composed of phenylene, biphenylene and carbon-carbon triple bonds, and poly(ethylene oxide) (PEO) with a degree of polymerization of 7 as coil segments. The molecular structures were characterized by H-1 NMR and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy. Investigation of the self-organization of the two molecules by means of differential scanning calorimetry, polarized optical microscopy and X-ray diffraction reveals that, for the coil-rod-coil molecular isomers, rod components of phenylene or biphenylene units linked together with PEO coil chains dramatically influence the self-assembly behavior in the bulk state. Structural isomers 1 and 2 self-assemble into lamellar structures in the crystalline state. In the liquid crystalline phase, molecule 1 containing phenylene units connected to coil segments self-organizes into a hexagonal perforated lamellar structure, while molecule 2 incorporating biphenylene units linked with coil segments self-assembles into a lamellar structure. (c) 2013 Society of Chemical Industry