Blending gelators to tune gel structure and probe anion-induced disassembly.

Jonathan A Foster,Gary J Cameron,Sam Ridgeway,Jonathan W Steed,Robert M Edkins,Neil Colgin,Andrew G Crawford,Andrew Beeby,Katharina Fucke,Todd B Marder,Steven L Cobb

doi:10.1002/chem.201303153

Jonathan A Foster, Gary J Cameron + Show 9 more

Open Access

https://doi.org/10.1002/chem.201303153

Copy DOI

Abstract

Blending different low molecular weight gelators (LMWGs) provides a convenient route to tune the properties of a gel and incorporate functionalities such as fluorescence. Blending a series of gelators having a common bis-urea motif, and functionalised with different amino acid-derived end-groups and differing length alkylene spacers is reported. Fluorescent gelators incorporating 1-and 2-pyrenyl moieties provide a probe of the mixed systems alongside structural and morphological data from powder diffraction and electron microscopy. Characterisation of the individual gelators reveals that although the expected α-urea tape motif is preserved, there is considerable variation in the gelation properties, molecular packing, fibre morphology and rheological behaviour. Mixing of the gelators revealed examples in which: 1) the gels formed separate, orthogonal networks maintaining their own packing and morphology, 2) the gels blended together into a single network, either adopting the packing and morphology of one gelator, or 3) a new structure not seen for either of the gelators individually was created. The strong binding of the urea functionalities to anions was exploited as a means of breaking down the gel structure, and the use of fluorescent gel blends provides new insights into anion-mediated gel dissolution.

Highlights

There has been a great deal of recent interest in the use of multi-component supramolecular gels as a means of creating responsive materials with enhanced functionalities and of tuning the properties of the resulting gels.[1]
We report the formation of both blended and phaseseparated gels from non-stoichiometric mixtures of structurally related gelators (1–7) derived from amino acids
On cooling from a hot solution, the glycine derivatives 1 and 3 form gels only in toluene, with gels formed from the hexylene spacer 3 being notably stronger than the butylene analogues

Summary

Introduction

There has been a great deal of recent interest in the use of multi-component supramolecular gels as a means of creating responsive materials with enhanced functionalities and of tuning the properties of the resulting gels.[1]. At a 1:4 ratio of a mixture of compounds 1 and 2, an additional set of peaks that match those of 2 form B are observed in addition to those of the blend, indicating the formation of an additional, separate network of 2 at high concentrations of the gelator.

Results

Conclusion