Photoresponsive Self‐Assembly and Self‐Organization of Hydrogen‐Bonded Supramolecular Tapes

Abstract

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.

Perylene bisimide organogels formed by melamine·cyanurate/barbiturate hydrogen-bonded tapes

“…The similar sheetlike morphologies have been reported for organogels composed of two-dimensionally organized supramolecular aggregates. 44,45 In contrast, the SEM image of 2 Á Bar displayed self-assembled structures with a grainy surface (Figure 7a). To confirm the presence of finer structures in nanoscopic scale, the surface of the xerogel of 2 Á Bar was analyzed by atomic force microscopy (AFM).…”

Challenges and breakthroughs in recent research on self-assembly

“…The latter characteristic is sometimes precious for dynamic control of assembly and disassembly processes. For example, Yagai et al reported photoresponsive self-assembly using a hydrogen-bond-directed cyclic hexamer (rosette) formed between melamine and barbituric acid derivatives (figure 56) [501,502]. In their system, azobenzene was selected as a photo-isomeric unit.…”

Experimental Study of the Mechanical Properties of a Novel Supramolecular Polymer Filament Using a Microtensile Tester Based on Electronic Balance

“…1 They have a wide range of applications in biomaterials, 2 -4 smart materials, 5,6 medicines, 7 -9 electronic devices, 10,11 and optical technologies. 12,13 Because of their highly organized nanostructures, supramolecular polymers present many advantages, such as molecular operability, cycle applicability, self-healing properties, and molecular recognition. 14 However, until now, most supramolecular polymer filaments are not free standing, which may bring out poor mechanical properties and may limit their applications.…”