Reentrant Gel–Sol–Gel Transition of a Lipophilic Co(II) Coordination Polymer

Nagatomi, Hisanori; Yanai, Nobuhiro; Kimizuka, Nobuo

doi:10.1246/cl.170881

Cited by 8 publications

(7 citation statements)

References 27 publications

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“…14 Phase re-entrance phenomena are sometimes observed in binary liquid solutions 1,21,22 and gases, [23][24][25] denaturation of proteins, [26][27][28] liquid crystals, [29][30][31] and gels. [32][33][34][35][36] This abnormal phase behaviour was rst observed over 100 years ago. 22 However, despite its role in important elds of biology and technology, 7,9,12,13 it received relatively limited attention, mainly from physicists who developed models that put this phenomenon in the right thermodynamics perspective.…”

Section: Introductionmentioning

confidence: 93%

Chirality dependent inverse-melting and re-entrant gelation in α-cyclodextrin/1-phenylethylamine mixtures

et al. 2020

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Section: Introductionmentioning

confidence: 93%

Chirality dependent inverse-melting and re-entrant gelation in α-cyclodextrin/1-phenylethylamine mixtures

et al. 2020

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“…In addition to organic salts, heat-set gelation can also be exhibited by coordination polymers, , organic/biological polymers, − inorganic complexes, and charge transfer complexes . None of these compounds melt or dissolve under conditions conducive to heat-set gelling.…”

Section: Heat-set Gelsmentioning

confidence: 99%

“…On the other hand, cooling a sol slowly increases the dimension while forming a gel condensate, which can be visualized by optical vortex formation. 17 When we prevent gel fibers from melting in the gelling solvent, the high-temperature polymorph can form a heat-set gel. 18−22 Azobenzene 23 or bipyridine 24 compounds possess an extremely rigid structure in comparison to alkane.…”

Section: Introductionmentioning

confidence: 99%

“…When we prevent gel fibers from melting in the gelling solvent, the high-temperature polymorph can form a heat-set gel. − Azobenzene or bipyridine compounds possess an extremely rigid structure in comparison to alkane. They behave as molecular motors , and face high energy barriers in torsion.…”

Section: Introductionmentioning

confidence: 99%

“…Incorporating such a rigid backbone prevents the PAD salts from reducing the symmetry smoothly; rather they jump from 2D crystal to 1D fibrous morphology . Both the heat-set gel , and liquid crystal systems , have their characteristic changes in packing patterns under a changing temperature. At a higher temperature, if the gelator can sustain the gel network and seize the gelling solvent, even sometimes beyond its boiling point, it exhibits a heat-set gelling property. − Once we can introduce a small functional unit inside the gelator backbone that does not allow the gelator to melt under heating, it generates the heat-set gel …”

Section: Introductionmentioning

confidence: 99%

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Introducing Dihedral Angle Torsion in a Flexible Dicarboxylic Acid: Evolution from a Sequential Symmetry Condensing Liquid Crystalline Gel to a Step-Halting Heat-Set Gel

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Crystal Growth & Design

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Through systematic molecular engineering, versatile properties can be incrementally introduced into supramolecular materials. Nonetheless, even a minor internal modification in the molecular backbone can outperform the conventional molecular engineering approach to fine-tune its corresponding supramolecular properties. A dicarboxylate salt, categorically primary ammonium dicarboxylate (PAD) salt derived from a flexible dicarboxylic acid such as adipic acid, imparts conformational flexibility to the salt in gelling solvents. This results in the exhibition of sequential symmetry condensing the liquid crystal gel against rising temperatures. Gentle heating can unzip van der Waals interactions, showcasing a gradual 2D to 0D phase-changing ability and generating liquid crystalline properties. Such gradual symmetry reduction quantifies the entropy enhancement during heating. On the other hand, the manipulation of dihedral angle torsion within a dicarboxylic acid backbone offers a means to tailor solubility. By increasing the dihedral angle torsion, the molecule loses alignment against the solvent's polarity or temperature, resulting in insolubility and conformational rigidity. Conversely, manipulating dihedral angle torsion within a dicarboxylic acid backbone provides a means to tailor solubility. Increasing dihedral angle torsion causes the molecule to lose alignment against the solvent's polarity or temperature, resulting in insolubility and conformational rigidity. Incorporating higher dihedral angle torsion energy, such as introducing an azo or ferrocene backbone into a dicarboxylic acid, renders the resulting molecule resistant to solubilization, even at high temperatures, resulting in a heat-set gel. This transformation turns sequential symmetry-condensing liquid crystal gelator molecules into two-step halting polymorphic state-based heat-set gelator molecules. This review demonstrates that a conventional functional group is not always mandatory for introducing supramolecular properties. Instead, a physical parameter, such as dihedral angle torsion, can be generated to finely tune the thermostatic properties in developing supramolecular heat-set or liquid crystal gels.

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Symmetry Breaking in Supramolecular Gel Condensation

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2024

Chemistry An Asian Journal

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Supramolecular condensation during cooling cycles often transitions through multiple metastable phases before achieving a stable crystalline state. Metastability arises from various competing parameters like symmetrical arrangement, and supramolecular bonding and manifests at different temperatures. Symmetrical physical arrangements can minimize vibrational energy and stabilize the systems at higher temperatures. Further cooling promotes directional supramolecular bonding, such as charge‐assisted hydrogen bonding, resulting in molecular periodicity within metastable structures. Frustration occurs when weaker van der Waals bonds form during further cooling, propagating perpendicularly to stronger one‐dimensional charge‐assisted hydrogen bonds and disrupting lateral periodicity in certain solvents. This makes parallel 1D fibers slidable, adding flexibility to the gel fiber. Eventually, some supramolecular systems attain thermodynamically stable crystalline states by perfectly arranging all the molecules. Throughout the process, metastability results from different symmetrical arrangements, and each rearrangement alters the supramolecular structure‘s symmetry, generating new physicochemical properties. Different supramolecular gels uniquely break symmetry, which can be monitored through various techniques. This perspective analyzes supramolecular thermoreversible, reverse thermal, liquid crystalline, thixotropic, and antisolvent‐induced gels to illustrate spontaneous symmetry reduction processes. Reaching a suprasymmetry condensate can classify big data and be applied in unconventional analogue computing or data storage.

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Reentrant Gel–Sol–Gel Transition of a Lipophilic Co(II) Coordination Polymer

Cited by 8 publications

References 27 publications

Chirality dependent inverse-melting and re-entrant gelation in α-cyclodextrin/1-phenylethylamine mixtures

Chirality dependent inverse-melting and re-entrant gelation in α-cyclodextrin/1-phenylethylamine mixtures

Introducing Dihedral Angle Torsion in a Flexible Dicarboxylic Acid: Evolution from a Sequential Symmetry Condensing Liquid Crystalline Gel to a Step-Halting Heat-Set Gel

Symmetry Breaking in Supramolecular Gel Condensation

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