Chemically programmed self-sorting of gelator networks

Abstract

Controlling the order and spatial distribution of self-assembly in multicomponent supramolecular systems could underpin exciting new functional materials, but it is extremely challenging. When a solution of different components self-assembles, the molecules can either coassemble, or self-sort, where a preference for like-like intermolecular interactions results in coexisting, homomolecular assemblies. A challenge is to produce generic and controlled 'one-pot' fabrication methods to form separate ordered assemblies from 'cocktails' of two or more self-assembling species, which might have relatively similar molecular structures and chemistry. Self-sorting in supramolecular gel phases is hence rare. Here we report the first example of the pH-controlled self-sorting of gelators to form self-assembled networks in water. Uniquely, the order of assembly can be predefined. The assembly of each component is preprogrammed by the pK a of the gelator. This pH-programming method will enable higher level, complex structures to be formed that cannot be accessed by simple thermal gelation.

Controlling supramolecular polymerization through multicomponent self‐assembly

“…295 Shifts of the apparent pKa value is a well-known phenomenon for polymeric weak acids, self-assembled fatty acids and amphiphilic block copolymers, [298][299][300][301][302][303][304][305] and has been used by many research labs in order to fine-tune the pH-triggered self-assembly of linear 306,307 and aromatic peptide amphiphiles. 85,[308][309][310][311] A similar effect has been reported by Matile and coworkers in the b-sheet directed self-assembly of poctiphenyl b-barrel pores embedded in lipid bilayers. 312 Weakening of the basic character of protonated lysine and histidine side chains (apparent pK a of 7 and 4.5, respectively), as well as a weakening of the acidic character of aspartic acid side chains (apparent pK a of 6) was observed.…”

Low-Molecular-Weight Gels: The State of the Art

“…In the final gel, we used fiber X-ray diffraction to show that the data for the self-sorted gel are essentially an overlay of the expected data from the two individual gelators. 97 Here, we note that in many cases, self-sorting is difficult to prove by microscopy.…”

“…We have shown that this approach can be applied to a number of mixtures provided that the apparent pK a values are around a unit apart. 97,98 We have proven that self-sorting occurs by a number of techniques. Sequential assembly can be shown by solution-phase NMR.…”

“…97,98,[100][101][102] It seems that the self-sorting is essentially pre-programmed into the system on the basis of the differences in the chemical structures.…”

“…In the final gel, we used fiber X-ray diffraction to show that the data for the self-sorted gel are essentially an overlay of the expected data from the two individual gelators. 97 Here, we note that in many cases, self-sorting is difficult to prove by microscopy.Although there are some systems where the two individual gelators happen to form self-assembled structures with sufficiently different diameters that microscopy can be used to show that there are two distinct populations, 99,100 in other cases, the structures formed are too similar to distinguish.We and others have reported a number of systems where self-sorting can be driven in this manner. 97,98,[100][101][102] It seems that the self-sorting is essentially pre-programmed into the system on the basis of the differences in the chemical structures.…”