Systems Chemistry and Dynamic Combinatorial Chemistry

The development of responsive, adaptive, and multitasking chemical systems is recognized as being of crucial importance to design the next generation of so-called “smart” materials. One may expect that such advanced artificial systems display several features which are present in – and thus inspired by – living systems. In particular, these new materials should ultimately combine three key properties of life which are the abilities to:

i) metabolize,
ii) mutate,
iii) self-replicate.

Part of our endeavors has been oriented toward the design of such advanced functional materials. In particular, we focus on molecular and supramolecular chemical systems based on mixtures of reversibly interacting molecules, coupled within networks of thermodynamic equilibria, and known as “dynamic combinatorial libraries”. We try to explain how the superimposition of combinatorial networks at different lengths scales of structural organization can provide valuable hierarchical dynamics for producing complex functional systems. In particular, a number of our results highlight why these libraries are of interest for the design of responsive materials, and how their functional properties can be modulated by various chemical and physical stimuli. We have also introduced examples in which these dynamic combinatorial systems can be coupled to kinetic feedback loops in order to produce self-replicating pathways that amplify a selected component from the equilibrated libraries.

These systems are of interest to go beyond the current generation of responsive materials, because their network topologies act as complex algorithms to process information. We propose a general overview of what could be defined as an autonomous, i.e. self-constructing material. Such a system should self-assemble among several possible molecular combinations in response to external information, and possibly self-replicate to amplify its functional response. Ultimately, this response can be the driving force for the self-assembly of the system that will in turn serve to transfer this initial information. Far from equilibrium, such synergistic processes might give rise to evolving – i.e. “information gaining” – systems which become more complex because they simply allow the surrounding potential energy to decrease faster, thanks to internal self-organization.

For an overview regarding the importance of chemistry and chemical networks in the origin of complex systems, see the excellent NASA-NSF workshop report.