On the Measurement of Phase Transition Temperatures in Physical Molecular Organogels

Térech, Pierre; Rossat, C.; Volino, F.

doi:10.1006/jcis.2000.6868

Cited by 82 publications

(64 citation statements)

References 40 publications

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“…Different physical methods refer to different microscopic processes (25). T t refers to the variation at the molecular level of the amounts of free and bound (in the gel) states of 1, possibly involving motions within fibrils without Table 1.…”

Section: Resultsmentioning

confidence: 99%

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

Sreenivasachary

Lehn

2005

Proc. Natl. Acad. Sci. U.S.A.

334

195

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The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven selforganization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel selfassembly involving three dynamic processes, two of supramolecular and one of reversible covalent nature. They extend constitutional dynamic chemistry to phase-organization and phasetransition events.dynamic combinatorial chemistry ͉ component selection ͉ supramolecular chemistry S upramolecular entities present the ability to reversibly modify their constitution through exchange and rearrangement of their molecular components because of the lability of the noncovalent interactions that hold them together (1, 2). Similar features may be imported into molecular species if reversible covalent bonds are introduced into their structure, allowing cleavage and formation of interatomic connections with fragment exchange under specific conditions. Thus, entities, capable of reversible modification of their constitution, define a constitutional dynamic chemistry on both the supramolecular and the molecular levels (3). Because the constitutional changes may be expected to respond to external factors, constitutional dynamic chemistry is the basis for the design and development of adaptive chemical systems. It generates constitutional dynamic libraries (CDLs) whose constituents are in dynamic equilibrium, such that they can exchange their components and express all of the entities that are potentially accessible through recombination by means of reversible covalent bonds and noncovalent interactions. The CDL may then adapt to (internal or) external phy...

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Section: Resultsmentioning

confidence: 99%

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

Sreenivasachary

Lehn

2005

Proc. Natl. Acad. Sci. U.S.A.

334

195

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“…Binary 12-HOA organogels were found to consist of a rigid fibrillar network with rigid junction zones. Both the fibrils and the junctions are crystalline 4,[8][9][10] and are generated via self-assembly of 12-HOA molecules, which is why the resulting gel network is called a self-assembled fibrillar network (SAFIN).…”

Section: Figmentioning

confidence: 99%

Gelled polymerizable microemulsions. Part 3 Rheology

et al. 2009

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The UCD community has made this article openly available. Please share how this access benefits you. Your story matters! (@ucd_oa) Some rights reserved. For more information, please see the item record link above. AbstractThis is the first report on the rheological properties of oil-gelled polymerizable bicontinuous microemulsions. The polymerizable base system consists of H 2 O / NIPAm / BisAm -ndodecane -C 13/15 E 5 (a technical grade n-alkyl polyglycol ether), where NIPAm denotes the monomer N-isopropylacrylamide and BisAm the cross-linker N,N′-methylene bisacrylamide.For the planned polymerization of the aqueous phase a scaffold is needed to preserve the structure of the templating microemulsion during the polymerization. This scaffold is supposed to be a gel, which was formed by adding the gelator 12-hydroxyoctadecanoic acid (12-HOA) to the oil phase of the microemulsion. The influence of the water-to-oil ratio , of the gelator concentration , and of the monomer concentration  on the rheological behavior of gelled microemulsions has been studied in detail. The most important result of the study at hand is the observation of a transition from a high viscous solution to a gel, i.e. from a transient to a permanent network, with increasing gelator concentration and increasing amount of the oil phase, respectively. In other words, it is only under well-defined conditions that an oil-gelled microemulsion is formed. * corresponding author: luis.magno@ucd.ie, phone/fax: +353-1-716-1691/1177 1 To review the final edited and published work see http://dx

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“…T gel was determined by a "dropping-ball method", [24] a small ball (about 100 mg) was placed on top of the hydrogel in a test tube (inner diameter 1.0 cm), which was slowly heated in a water bath with the increasing rate of 1 ℃/min. The T gel was defined as the average value that the ball begins to fall and falls to the bottom of the test tube.…”

Section: T Gel Measurementsmentioning

confidence: 99%

Electro-responsive Binary Hydrogels Based on Calixarene and Viologens

Wang¹,

Guo²,

Zhang³

et al. 2012

Acta Chim. Sinica

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We built several supramolecular binary hydrogels based on tetra-proline modified calix[4]arene (TPC) and various viologens. The obtained results show that the TPC gelation is mostly achieved with viologen bromides in acidic condition. The variation of viologen side-chains has notable impact on the properties of the hydrogels, such as the gel-sol transition temperature (T gel ) and morphology, which were evaluated by the combination of dropping-ball method, atomic force microscopy and scanning electron microscopy. The prepared hydrogels are significantly electro-responsive, as well as chemical-sensitive, pH-sensitive and thermo-reversible.

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On the Measurement of Phase Transition Temperatures in Physical Molecular Organogels

Cited by 82 publications

References 40 publications

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

Gelled polymerizable microemulsions. Part 3 Rheology

Electro-responsive Binary Hydrogels Based on Calixarene and Viologens

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