Supramolecular networks

Kurt Nikolaus Wiegel

Abstract

This work describes the creation of a series of supramolecular networks. The creation of supramolecular liquid crystalline networks is a relatively recent area of study. In many of these cases, however, the network-forming event is also a mesogen-forming event. If the network-forming event is not mesogenic, or is even deleterious to liquid crystallinity, the change in properties would be profound. The effect of introducing a reversible crosslinker into a supramolecular mesogenic polymer, particularly when the network and the mesogen would be in competition for the hydrogen bond donor is presented here. A macroscale phase-separation is observed, producing mesogen-rich and netpoint-rich domains. This is the first reported case of a macroscale rearrangement forcing phase exclusion. Additionally, a study of such effects on covalent systems, in which macroscale rearrangement is not possible, is also described. An intensive study of the morphology of such networks has not yet been undertaken. In many cases, the networks formed have been of a multiple-hydrogen bond nature, and closely mimic their covalent analogs. Using a single hydrogen-bond (such as an acid/pyridyl association) as the network forming event, the lability effect induced by that hydrogen bond produces a profound effect on the properties of these materials. In many cases, a "memory effect" is created, in which the network can rearrange on a macroscopic level when perturbed (by thermal treatment, for example) and then, over time, revert to its original morphology. This effect is seen in several of the networks created both by varying the acid and pyridyl molecules involved.