Emergence of low-symmetry foldamers from single monomers

Self-assembly is a powerful method to obtain large discrete functional molecular architectures. When using a single building block, self-assembly generally yields symmetrical objects in which all the subunits relate similarly to their neighbours. Here we report the discovery of a family of self-constructing cyclic macromolecules with stable folded conformations of low symmetry, which include some with a prime number (13, 17 and 23) of units, despite being formed from a single component. The formation of these objects amounts to the production of polymers with a perfectly uniform length. Design rules for the spontaneous emergence of such macromolecules include endowing monomers with a strong potential for non-covalent interactions that remain frustrated in competing entropically favoured yet conformationally restrained smaller cycles. The process can also be templated by a guest molecule that itself has an asymmetrical structure, which paves the way to molecular imprinting techniques at the level of single polymer chains. The majority of discrete structures obtained by self-assembly possess high symmetry, and thus low complexity: all subunits relate to their neighbours in a similar manner. Now, the spontaneous formation of complex low-symmetry assemblies produced from a single building block has been demonstrated using a systems chemistry approach. The single building block oligomerizes to form specific homomeric cyclic macromolecules that adopt a folded conformation.