Low Molecular Weight Gelators for Organic Solvents

Esch, Jan H. van; Schoonbeek, Franck S.; Loos, Maaike de; Veen, E. Marc; Kellogg, Richard M.; Feringa, Bernard

doi:10.1007/978-94-011-4554-1_14

Cited by 37 publications

(6 citation statements)

References 70 publications

(56 reference statements)

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“…These soft materials are formed by self-assembly of low-molecular-mass gelators (LMMGs) through noncovalent forces, such as hydrogen-bonding (H-bonding), electrostatic forces, π–π stacking, and London dispersion forces. − These weak forces cause molecular interactions among the gelator molecules in the molecular level to form one-dimensional (1D) aggregate at the micrometer length scale, which upon further entanglement led to the formation of three-dimensional (3D) network structure causing entrapment of solvents . The macroscopic flow of the solvents is thus prevented by the 3D network structures through surface tension and capillary forces . To date, numerous efforts have been made to understand the mechanism of formation of supramolecular gels.…”

Section: Introductionmentioning

confidence: 99%

“…12 The macroscopic flow of the solvents is thus prevented by the 3D network structures through surface tension and capillary forces. 13 To date, numerous efforts have been made to understand the mechanism of formation of supramolecular gels. Literature reports reveal that factors that induce/enhance gelation are chirality, H-bonding, π−π stacking, van der Waals interaction, etc.…”

Section: Introductionmentioning

confidence: 99%

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Ultrasound-Induced Gelation of Organic Liquids by l-Cysteine-Derived Amphiphile Containing Poly(ethylene glycol) Tail

Mahapatra

2015

Langmuir

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Amphiphile containing l-cysteine covalently linked with poly(ethylene glycol) (PEG) chain (PEG360-Cys) was observed to produce transparent gel at room temperature in polar aprotic solvents not only by heating-cooling (HC) but also when subjected to ultrasound (US). It was observed that a suspension of PEG360-Cys when treated with US readily formed gel at much lower critical gelation concentration. US irradiation has been established to control the gel properties at the molecular level. The morphological change of the organogels produced by the HC and US methods was confirmed from scanning as well as transmission electron microscopy. The organogels produced by the two external stimuli (HC and US) were characterized in detail by FTIR spectroscopy, differential scanning calorimetry, and rheology to shed light on the molecular packing during gelation. It is important to note that the US-induced organogels showed almost 13-fold increase in gel strength compared to the organogels obtained by the HC method. Further, US-induced gels were found to be thermally more stable than the heat-set gels. All these studies clearly demonstrate that hydrogen-bonding interaction is the main driving force for both the gelation processes, but the mode of hydrogen bonding at the molecular level is different.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ultrasound-Induced Gelation of Organic Liquids by l-Cysteine-Derived Amphiphile Containing Poly(ethylene glycol) Tail

Mahapatra

2015

Langmuir

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“…Recently, exploitation of new organic gelators which can gelate various organic solvents has become an active area of research endeavor. − These organogels are of particular importance and interest because of the essential difference from well-known polymer gels in the gelation mechanism and the potential applications. More recently, it was found that certain cholesterol derivatives can gelate even tetraethoxysilane (TEOS) which can be used to produce silica by sol−gel polymerization .…”

mentioning

confidence: 99%

Creation of Both Right-Handed and Left-Handed Silica Structures by Sol−Gel Transcription of Organogel Fibers Comprised of Chiral Diaminocyclohexane Derivatives

et al. 2000

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A diversity of supramolecular structures can be created, not only in nature but also in artificial systems, by self-assembly of designed "organic" building blocks. 1 One may consider that this phenomenon is inherent to organic materials. In contrast, creation of such diverse supramolecular structures from "inorganic" materials seems to be very difficult or nearly impossible. The sole method, if any, would be to design such inorganic materials under a template effect of organic supramolecular aggregates. 2 Recently, exploitation of new organic gelators which can gelate various organic solvents has become an active area of research endeavor. 3-7 These organogels are of particular importance and interest because of the essential difference from well-known polymer gels in the gelation mechanism and the potential applications. More recently, it was found that certain cholesterol derivatives can gelate even tetraethoxysilane (TEOS) which can be used to produce silica by sol-gel polymerization. 8 Very interestingly, it was shown that sol-gel polymerization of gelated TEOS solutions affords silica with a novel hollow fiber structure, because the organogel fibers act as a template in the TEOS polymerization process which, after calcination, result in an hollow tube. 8,9 This organic-inorganic transcription process forms an interesting analogy the formation of fossil remains. The finding tempted us to test whether the helical structure in organogel fibers may be also transcribed into inorganic silica, which would be a completely new way to transcribe chiral information into an inorganic material.Here, we report on a novel creation method of helically structured silica by sol-gel transcription in chiral diaminocyclohexane-based organogel systems. Very interestingly, we have found that right-and left-handed helical silica structures can be created by transcription of right-and left-handed structures in the organogel fibers, respectively. Although several inorganic materials with some helical structure have been reported, 2a,10 these have been produced utilizing a specific crystallization method or a mechanical method. These methods are quite different from our fine chiral transcription method utilizing chiral organogel fibers. To the best of our knowledge, this is the first example of the creation of both "right-and left-handed helical silica structures" by a sol-gel transcription method.Compounds 1-4 were synthesized using methods which are similar to described previously. 3,8 The gelation ability of 2 and 4 was estimated for 10 different organic solvents (5.00 × 10 -2 mol dm -3 ). 5 Neutral 1 and 3 can gelate alcohols, aprotic, and apolar solvents, indicating that they act as versatile gelators of organic solvents. On the other hand, cationic 2 and 4 can gelate acetonitrile, THF, DMSO, and DMF, indicating that the gelation ability is deteriorated by introduction of cationic charges. However, it can be seen that the gelation ability for aprotic solvents is excellent. Since the presence of the cationic charge in organog...

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“…Furthermore, twisting of the fibers was observed only in the sol of 0.5 wt% DIBA in hexylbenzene. These results indicate that the fiber widths and degrees of twisting are dependent on the nature of the solvent used for gelation [35]. No twisting of fibers and larger widths were observed with octane as the gelation solvent.…”

Section: Morphologies From Polarized Optical Micrographs and Transmis...mentioning

confidence: 71%

Molecular and Aggregate Structural, Thermal, Mechanical and Photophysical Properties of Long-Chain Amide Gelators Containing an α-Diketo Group in the Presence or Absence of a Tertiary Amine Group

Grover

Brothers

Weiss

2022

Gels

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Three structurally related gelators, each containing octadecyl chains, an α-diketo group at the 9,10 positions, and each with a different N-amide group—isobutyl (DIBA), isopentyl (DIPA) or N-(2-(dimethylamino)ethyl) (DMEA)—have been synthesized. Their neat structures as well as the thermal mechanical, and photophysical properties in their gel states with various liquids have been investigated. The gelator networks of DIBA and DIPA in octane, hexylbenzene and silicone oil consist of bundles of fibers. These gels are partially thixotropic and mechanically, thermally (to above their melting or silicone oil gelation temperatures), and photophysically stable. They are mechanically and thermally stronger than the gels formed with DMEA, the gelator with a tertiary amine group. The lone pair of electrons of the tertiary amine group leads to an intra-molecular or inter-molecular charge-transfer interaction, depending on whether the sample is a solution, sol, or gel. Neat, solid DMEA does not undergo the charge-transfer process because its amino and diketo groups are separated spatially by a large distance in the crystalline state and cannot diffuse into proximity. However, the solution of DIPA upon the addition of triethylamine becomes unstable over time at room temperature in the dark or (more rapidly) when irradiated, which initiates the aforementioned charge-transfer processes. The eventual reaction of the gelators in the presence of a tertiary amine group is ascribed to electron transfer from the lone-pair on nitrogen to an α-diketo group, followed by proton transfer to an oxygen atom on the anion radical of the α-diketo group from a methyl or methylene group attached to the nitrogen atom of the cation radical. Finally, the formation of an α-diketyl radical leads to irreversible electronic and structural changes that are observed over time.

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Low Molecular Weight Gelators for Organic Solvents

Cited by 37 publications

References 70 publications

Ultrasound-Induced Gelation of Organic Liquids by l-Cysteine-Derived Amphiphile Containing Poly(ethylene glycol) Tail

Ultrasound-Induced Gelation of Organic Liquids by l-Cysteine-Derived Amphiphile Containing Poly(ethylene glycol) Tail

Creation of Both Right-Handed and Left-Handed Silica Structures by Sol−Gel Transcription of Organogel Fibers Comprised of Chiral Diaminocyclohexane Derivatives

Molecular and Aggregate Structural, Thermal, Mechanical and Photophysical Properties of Long-Chain Amide Gelators Containing an α-Diketo Group in the Presence or Absence of a Tertiary Amine Group

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