Controlling the network type in self-assembled dipeptide hydrogels

Colquhoun, Catherine; Draper, Emily R.; Schweins, Ralf; Marcello, Marco; Vadukul, Devkee M.; Serpell, Louise C.; Adams, Dave J.

doi:10.1039/c6sm02666d

Cited by 72 publications

(119 citation statements)

References 51 publications

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“…At this point, the gels actually become weaker as the concentration of the 2NapFF is increased. 72 This counter-intuitive observation can be explained in line with the observation of liquid crystalline phases, which presumably result from lateral aggregation of the worm-like micelles at these higher concentrations. As more 2NapFF is added, the lateral association increases, rather than there simply being more and more worm-like micelles present that can entangle.…”

Section: Process Of Assemblymentioning

confidence: 51%

“…72 The apparent pK a of the terminal carboxylic acid of 2NapFF is around 6.0. 86 This is perhaps surprisingly high for the terminal carboxylic acid of a dipeptide, but this is a common observation for this kind of gelator.…”

Section: Process Of Assemblymentioning

confidence: 99%

“…For example, 2NapFF can form hydrogels by using a range of triggers and is an excellent example of a complicated system that exemplifies how the process of assembly matters ( Figure 5). 72 First, this LMWG can be dissolved in an organic solvent such as DMSO. Addition of water results in a gel.…”

Section: Process Of Assemblymentioning

confidence: 99%

“…On decreasing the pH, the core is lost, and the scattering data can best be fit to an elliptical cylinder. 72 This could be interpreted as the structures re-organizing, or it is also possible that the initial structures fall apart and then new structures form. One interesting observation is that the gels formed at high pH by addition of a calcium salt decrease in gel strength dramatically when the pH is decreased, and then become stronger again as the pH drops below the pK a .…”

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confidence: 99%

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

Draper

Adams

2017

Chem

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Low-molecular-weight gels are currently a hugely important class of materials that are attracting significant interest. These gels are formed when small molecules self-assemble into one-dimensional structures that entangle and cross-link to form a network that is capable of immobilizing the solvent. Here, we critically discuss the current state of the art and highlight two key areas where we believe there is significant untapped potential. The first is the observation that the properties of the gels are highly process dependent, which means that it is possible to access materials with very different properties from a single gelator. Second, using multiple gelators offers the opportunity to prepare materials with a high degree of information content and with a wider range of properties. We aim to spark thought and discussion on these aspects. INTRODUCTIONLow-molecular-weight gels (LMWGs), or supramolecular gels, are a fascinating and useful class of material. The gels arise from the self-assembly of small molecules into long, anisotropic structures, most commonly fibers. [1][2][3][4][5] At a sufficiently high concentration, these fibers entangle or otherwise form cross-links, leading to the network that is able to immobilize the solvent through surface tension and capillary forces. 1,2 These gels differ from permanently covalently cross-linked polymer gels because the cross-linking can be reversed by the input of energy, for example, by heating. 6 LMWGs have been around for many years but are receiving considerable current interest. 4 They are also used in industrial products, 7 although this seems rarely discussed in the academic literature.In addition to the industrial applications, many recent advances and uses are being described. [8][9][10][11][12] The specific self-assembly leading to gel formation can be exploited. For example, the fiber formation is a result of molecular stacking, meaning that the self-assembly leads to aggregates that can be suitable for optoelectronic applications. 13,14 The ready reversibility of gelation can be exploited, for example, to release cells from gels on demand in a manner that does not lead to cell death. 15 Ready gel formation by a simple trigger can also be used to allow easy and efficient gel loading. [16][17][18] Unsurprisingly, therefore, there is significant interest in these materials ( Figure 1). This is a fascinating area and in many ways holds attention because of the difficulties in probing and understanding the gels. The gels arise from assembly across many length scales, and understanding all of these is difficult. At the molecular level, the molecules must interact in a manner that leads to the formation of suitable aggregates that can eventually entangle. Thus, one-dimensional growth must be favored. From this perspective, it is very frustrating that it is often extremely difficult to predict whether a molecule will form a gel or not; indeed, gelation has been described as an empirical science. 4 Structurally similar small molecules can exhibitThe Bigger Pict...

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Section: Process Of Assemblymentioning

confidence: 51%

Section: Process Of Assemblymentioning

confidence: 99%

Section: Process Of Assemblymentioning

confidence: 99%

mentioning

confidence: 99%

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

Draper

Adams

2017

Chem

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538

469

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“…A homogeneous gel is formed after standing overnight (initially, local gelation occurs where the salt solution contacts the 2NapFF solution). As described previously,2a addition of a solution of CaCl 2 to an as‐prepared solution of the gelator leads to formation of a turbid gel. A significantly more transparent gel is formed if the solution of CaCl 2 is added to a solution removed immediately after the heating step, or to a pre‐heated solution that has been allowed to cool and rest at room temperature (Figure 4 a).…”

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confidence: 93%