Engineering of Small Molecule Organogels by Design of the Nanometer Structure of Fiber Networks

Li, Jingliang; Liu, Xiang Yang; Strom, C.S.; Xiong, Jun Ying

doi:10.1002/adma.200500694

Cited by 73 publications

(78 citation statements)

References 25 publications

(5 reference statements)

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“…Similar spectral shifts were also found in other gel systems (Table 3). It is a little bit surprising that the direction of the spectral shifts of MaLC system is different from other gel systems (Table 3), indicating that a different aggregation mode might be adopted by this system [48]. Similar phenomena were reported by our group before [22].…”

Section: Ft-ir Spectroscopysupporting

confidence: 80%

Preparation of dicholesteryl-derivatives: The effect of spatial configuration upon gelation

Yan

Zhang

et al. 2012

Chin. Sci. Bull.

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To investigate the effect of spatial configuration on the gelation properties of low molecular mass gelators (LMMGs), four novel di-cholesteryl derivatives have been specially designed and synthesized by introducing the cis-/trans-isomers of butene diacid and the optical isomers of D/L-phenylalanine into the linker between two cholesteryl moieties. These isomers have been denoted as MaDC, FaDC, MaLC and FaLC, respectively. The gelation properties of the compounds were examined in 26 organic solvents, and it was found that the trans-configuration is more favorable for the gelation, but the chirality of the linker shows little effect to the gelation. FaDC has the strongest gelation ability among the four isomers. Interestingly, FaDC and FaLC display phase-selective gelation of benzene, toluene and xylene from their mixtures with water at room temperature, which establishes a foundation for the purification of water contaminated by oil or aromatic solvents. SEM and CD spectroscopy studies revealed that the spatial configuration of the linkers of the gelators affects significantly the aggregation mode, the morphologies and the chirality of the network of the gels. Moreover, the different aggregation behaviors also have an impact on mechanical properties of the gels, which are consistent with the results from rheological studies. Furthermore, temperature-and concentration-dependent 1 H NMR and FTIR measurements demonstrated that intermolecular hydrogen bonding and - stacking are the main driving forces for the formation of the gels.

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Section: Ft-ir Spectroscopysupporting

confidence: 80%

Preparation of dicholesteryl-derivatives: The effect of spatial configuration upon gelation

Yan

Zhang

et al. 2012

Chin. Sci. Bull.

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“…Temperature is a key parameter; most LMWGs melt and the range of temperatures over which the gel is stable is variable and again hard to predict and understand. Additives are known to both hinder and promote gelation, 35,36 often again without a detailed understanding. In some cases, it has been shown that salts can affect aggregation on the basis of the Hofmeister series, 37 and certain polymer additives have been shown to affect gelation by specific interactions ( Figure 2B).…”

Section: Introductionmentioning

confidence: 99%

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

Draper

Adams

2017

Chem

514

469

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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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“…The choice is also motivated by the consideration that a properly chosen surfactant will selectively and strongly adsorb on the tip or side surface of the growing crystalline fibers, disrupting the structural match between new layers and the parent fibers, and lead to the side or tip branching by the mechanism of crystallographic mismatch branching. [26][27][28][29] For these reasons, this nonionic surfactant, Span 20, was chosen as a branching promoter and a topolical modification agent to improve the gel performance and reconstruct the topology of GP-1/PG fiber network in our experiments. We will investigate and demonstrate how the overall topology of GP-1 fiber networks can be modified by Span 20, by weakening or strengthening the solid-like quality of soft materials, depending on the surfactant concentration.…”

Section: Resultsmentioning

confidence: 99%

“…As j can be measured from the SEM images, it www.afm-journal.de can be used to quantify to some extent the fiber network structure. [27] The smaller the correlation length j, the shorter the fiber segments, and the higher the fiber branching density. Figure max is about 9 Â 10 5 Pa, three times compared with that without any surfactants.…”

Section: Resultsmentioning

confidence: 99%

“…nonionic surfactant, polyoxyethylene sorbitan monooleate (Tween 80) was used to promote fiber branching in modifying the fiber network and enhancing the mechanical properties of a low molecular organogel. [27] Here, we will report a robust approach as illustrated in Scheme 1 in producing new supramolecular functional materials based on the reconstruction and modification of the architecture of three-dimensional interconnecting selforganized nanofiber networks with the aid of a so-called topological modifier. The system is N-lauroyl-L-glutamic acid din-butylamide (GP-1) in the solvent propylene glycol (PG).…”

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confidence: 99%

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Producing Supramolecular Functional Materials Based on Fiber Network Reconstruction

Tang

Liu

Strom

2009

Adv Funct Materials

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Here, the creation of new supramolecular functional materials based on the reconstruction of three‐dimensional interconnecting self‐organized nanofiber networks by a surfactant is reported. The system under investigation is N‐lauroyl‐L‐glutamic acid di‐n‐butylamide in propylene glycol. The architecture of networks is implemented in terms of surfactants, e.g. sorbitan monolaurate. The elastic performance of the soft functional material is either weakened or strengthened (up to 300% for the current system) by reconstructing the topology of a fiber network. A topology transition of gel fiber network from spherulite‐like to comb‐like to spherulite‐like is performed with the introduction of this surfactant. The Span 20 molecules are selectively adsorbed on the side surfaces of the crystalline fibers and promote the nucleation of side branches, giving rise to the transformation of the network architecture from spherulite‐like topology to comb‐like topology. At high surfactant concentrations, the occurrence of micelles may provide an increasing number of nucleation centers for spherulitic growth, leading to the reformation of spherulite‐like topology. An analysis on fiber network topology supports and verifies a perfect agreement between the topological behavior and the rheological behavior of the functional materials. The approach identified in this study opens up a completely new avenue in designing and producing self‐supporting supramolecular functional materials with designated macroscopic properties.

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Engineering of Small Molecule Organogels by Design of the Nanometer Structure of Fiber Networks

Cited by 73 publications

References 25 publications

Preparation of dicholesteryl-derivatives: The effect of spatial configuration upon gelation

Preparation of dicholesteryl-derivatives: The effect of spatial configuration upon gelation

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

Producing Supramolecular Functional Materials Based on Fiber Network Reconstruction

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