Biology often uses hierarchical self-assembly to produce complex functional structures from smaller components. At each level of this stepwise process, non-covalent interactions bring together the subunits of a lower level of complexity, using the information encoded in their structures. Applying this approach to synthetic systems represents a formidable challenge, because it requires a high degree of command of non-covalent interactions. In this tutorial review, recent developments in the hierarchical self-assembly of discrete columnar aggregates are discussed.

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The concept of polymerization-induced phase separation with hydrogen-bonded supramolecular polymers was investigated by the photopolymerization of films containing mixtures of supramolecular polymer 1a or 1b and varying amounts of monoacrylate and diacrylate with UV-A (320−400 nm) radiation (5 W/cm2) for 0.3 s. The extent of the phase separation after photopolymerization was determined by differential scanning calorimetry and scanning electron microscopy, which showed that film 1 containing no diacrylate is macrophase-separated, while films 2 and 3 containing 17.0 or 42.5% diacrylate are microphase-separated. Increasing the amount of diacrylates has a strong influence on the morphology development, as it decreases the length scale of the phase separation by shortening the time available before vitrification sets inin this way decreasing the crystallinity of the supramolecular phase. Tensile tests and DMTA measurements showed that the mechanical properties of the films containing the hydrogen-bonded supramolecular polymers are comparable to those films containing covalent high molecular weight polymers.

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