Two-component gel-phase materials--highly tunable self-assembling systems.

In the past 10 years, the molecular self-assembly and network formation of small molecule gelators has become one of the most active frontiers of the emergent area of nanochemistry. Increasingly, research efforts have begun to focus on multicomponent gelators, which rely on the initial interaction of distinct individual components to form a complex that subsequently self-assembles into a fibrous supramolecular polymer. In true two-component systems, an individual component can be present in isotropic solution, and only on addition of the second component will a gel actually form. In some cases, however, two-component gels are reported in which the second component significantly modifies the behaviour of a known gelator. Both systems are discussed in this article. The additional level of supramolecular control in the hierarchical self-assembly of two-component gels confers exquisite tunability and controllability. Functionality can be readily built into the material by simple variation of one of the individual components. This article discusses the key approaches used to control self-assembly by manipulating single molecular-recognition events and illustrates how controlling the transcription of information from the molecular to the macroscopic level by the simple addition of a second component allows complex functional materials to be selectively assembled from simple building blocks.