Naphthalene dipeptides have been shown to be useful low-molecular-weight gelators. Here we have used a library to explore the relationship between the dipeptide sequence and the hydrogelation efficiency. A number of the naphthalene dipeptides are crystallizable from water, enabling us to investigate the comparison between the gel/fiber phase and the crystal phase. We succeeded in crystallizing one example directly from the gel phase. Using X-ray crystallography, molecular modeling, and X-ray fiber diffraction, we show that the molecular packing of this crystal structure differs from the structure of the gel/fiber phase. Although the crystal structures may provide important insights into stabilizing interactions, our analysis indicates a rearrangement of structural packing within the fibers. These observations are consistent with the fibrillar interactions and interatomic separations promoting 1D assembly whereas in the crystals the peptides are aligned along multiple axes, allowing 3D growth. This observation has an impact on the use of crystal structures to determine supramolecular synthons for gelators.

This article describes the synthesis and surpamolecular assembly of polyurethane-based elastomers. Triple hydrogen bonding between novel amidoisocytosine (AIC) and ureidoimidazole (UIM) motifs is used to promote assembly of the material. The material comprises an amorphous phase derived from a telechelic diol and a hard crystalline phase that comprises the supramolecular end groups. The use of a heterocomplementary hydrogen bonding interaction results in two unique features: (1) assembly of the elastomer occurs only in the presence of both components, and (2) different feed ratios used during synthesis allow the materials properties to be tuned as the stoichiometries of the components found in the amorphous and crystalline phases of the material are varied. The approach hence offers supramolecular control over materials properties and results in materials that can be melted and therefore processed at lower temperature compared to standard covalent elastomers.

As a class of materials, supramolecular polymers represent an exciting area of advanced materials research. The combination of unique properties, easy synthesis and response to the environment or external and temporal stimuli makes them important as a focus for the next generation of materials. Understanding and manipulating the non-covalent interactions leading to polymer assembly allows control over properties by selecting specific building blocks with well-understood non-covalent chemistry from an established toolkit. This allows assembly of defined and easily manipulated architectures, where physical characteristics similar to conventional high-molecular-weight polymers can be realized. Herein, we describe recent studies of the self-assembly of polyurethane-based supramolecular materials.

A series of hydrogen-bonding motifs are shown to be capable of both high-fidelity and promiscuous molecular recognition behaviour. This gives rise to self-sorting and therefore well defined product distributions for up to four sequential phases of building block composition. Inclusion of a hydrogenbonding motif that becomes capable of molecular recognition only upon photo-cleavage, extends the number of phases in the cascade to five. This supramolecular system thus reproduces multiple features of biological signalling cascades including the ability to switch between successive states comprising multiple well-defined complexes and triggered modification of molecular recognition preferences.

A solvent free ball-milling method for the synthesis of small molecule and oligomeric carbamates is described that is applicable to supramolecular polymer synthesis.