How should multicomponent supramolecular gels be characterised?

Emily R Draper,Dave J Adams

doi:10.1039/c7cs00804j

Emily R Draper, Dave J Adams

Open Access

https://doi.org/10.1039/c7cs00804j

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Abstract

Low molecular weight gels, or supramolecular gels, are formed when small molecules self-assemble into fibrous structures. Above a critical concentration, the entanglement and cross-linking of these structures leads to the formation of a self-supporting gel. There are many examples where a single component is used to form such gels. There is however an ever-increasing interest in using multiple components. Here, if each component is able to form a gel by itself, a range of fibre types are possible, formed by either random or specific associations between the low molecular weight gelators (LMWG). The properties of the networks will depend on how the LMWG assemble into the primary fibrous structures and then how these primary structures entangle. As such, to understand these gels, it is necessary to understand the networks across multiple length scales. Here, we discuss the current state of the art, the effectiveness of the different techniques that have been used, and hopefully provide the impetus for the field to move away from the cartoon-level discussion of assembly.

Highlights

Gels can be formed by the self-assembly of small molecules called low molecular weight gelators (LMWGs).[1,2,3] To form the gels, the LMWG assemble into long fibres, which cross-link in some manner, either by entanglement or branching for example, to form a network
Assuming that the overall self-assembly process still leads to the formation of fibres, the LMWG can interact to lead to ordered fibres containing both gelators (e.g. Fig. 1a), or randomly to form fibres that contain random amounts of both LMWG (Fig. 1b)
Whilst the fibres formed from the two LMWGs formed apparently different fibres when alone, the microscopy for the multicomponent system showed a range of fibres which could not be categorically assigned

Summary

Introduction

Gels can be formed by the self-assembly of small molecules called low molecular weight gelators (LMWGs).[1,2,3] To form the gels, the LMWG assemble into long fibres, which cross-link in some manner, either by entanglement or branching for example, to form a network. For a mixture of dipeptide-based LMWGs that we were able to show formed a self-sorted system by other techniques, it was extremely difficult to ascertain this by microscopy.[23] Whilst the fibres formed from the two LMWGs formed apparently different fibres when alone, the microscopy for the multicomponent system showed a range of fibres which could not be categorically assigned.

Results

Conclusion