Lateral association of cylindrical nanofibers into flat ribbons triggered by "molecular glue".

The development of novel functional materials based on selfassociating block molecules has received a great deal of attention because of their potential for the construction of elaborately defined supramolecular nanostructures. For example, the incorporation of a rigid aromatic segment into amphiphilic molecular architectures enhances their capability to form aggregates, leading to the assembly of a variety of nanostructures including spheres, toroids, ribbons, and tubes, depending on the structure of the component molecules. Among the nanostructures formed by the self-assembly of specifically designed molecules, a 1D fibrillar assembly has proved to be particularly interesting for applications such as nanowires, gels, and biomemetic systems. The scope of 1D structures with stimulus-responsive properties is likely to be further extended towards the area of smart nanoscale materials. We have shown that the conformational change that coordination polymers undergo upon counteranion exchange gives rise to a significant structural change from elongated fibers into discrete aggregates, which results in sol–gel interconversion. We have also shown that T-shaped aromatic amphiphiles based on oligoether dendrons selfassemble into thermoresponsive nanofibers by the reversible dehydration of external oligoether chains. We have recently demonstrated that structural inversion of the cylindrical core formed by the self-assembly of wedgecoil block molecules based on a hydrophobic branched segment led to a reversible switching between rigid rodlike and flexible coil-like aggregates that is triggered by solvent polarity. In particular, the formation of flexible coil-like cylindrical aggregates in aqueous solution is attributed to the aggregation of branched hydrophobic chains into amorphous cylindrical cores. Thus, the addition of aromatic guest molecules into the hydrophobic core should force the Y-shaped aromatic segments, which are radially distributed, to be arranged in a more dense, parallel packing and so bind the guest efficiently. This rearrangement could result in a structural change of the 1D assembly into larger aggregates to maximize the parallel packing of the aromatic segments (Figure 1). The guest molecules could then be considered as