Synthesis and self-assembly of oligomers containing cruciform 9,10-bis(arylethynyl)anthracene unit: formation of supramolecular nanostructures based on rod-length-dependent organization

Conjugated rod-coil molecules, incorporating flexible and rigid blocks, have a strong affinity to self-organize into various supramolecular nanostructures in the bulk state.In this study, we report synthesized oligomers containing cruciform 9,10-bis(arylethynyl)anthracene units and characterized their self-assembly behavior. The molecular structures were characterized with 1H, 13C NMR, and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. An investigation of the supramolecular nanostructures of these molecules using differential scanning calorimetry, thermal polarized optical microscopy, and small-angle X-ray scattering revealed that the rod length of coil-rod-coil molecules with identical rod to coil volume ratios dramatically influences self-assembly behavior in the bulk state. Molecules 2 and 3 with relatively longer rod lengths self-assemble into lamellar structures in the solid state, whereas, molecules 1 and 4 self-assemble into two-dimensional (2-D) oblique columnar structures in the liquid crystalline phase, in addition, on heating, molecule 1 transforms from the oblique columnar phase to the nematic phase.

Graphical abstractDownload full-size imageConjugated coil-rod-coil oligomers containing cruciform 9,10-bis(arylethynyl) anthracene units with different molecular lengths, but identical rod to coil volume ratios, were synthesized. An investigation of the supramolecular nanostructures of these molecules revealed that the rod length of coil-rod-coil molecules with identical rod to coil volume ratios, dramatically influences the self-assembly behavior in the bulk state.