Supergelation via Purely Aromatic π–π Driven Self-Assembly of Pseudodiscotic Oxadiazole Mesogens

Sivadas, Aneesh P.; Kumar, N. S. Saleesh; Prabhu, Deepak D.; Varghese, Shinto; Prasad, S. Krishna; Rao, D. S. Shankar; Das, Suresh

doi:10.1021/ja500607d

Cited by 53 publications

(28 citation statements)

References 70 publications

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“…%, thus qualifying themselves as ‘supergelators’ . There are many reports on supergelators, which are assisted by strong intermolecular attractive forces likes H‐bonding, but supergelation exclusively promoted by π‐π interaction is very rare . m ‐Connected polycatenars did not show gelation in hydrocarbon solvents, the reason behind this observation may be their bent structure and high solubility in the aliphatic solvents.…”

Section: Resultsmentioning

confidence: 99%

Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism

et al. 2016

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Two series of five ring polycatenars, which vary from each other with respect to the position of connection to the central benzene ring are reported. The overall shape of the molecule plays a major role than the number of flexible tails in the periphery in dictating the self-assembly (liquid crystallinity and gelation) and the photophysical behavior. Tetracatenars were crystalline and meta-substituted compounds exhibited reduced tendency to stabilize the mesophase. In the para-substituted series, all the hexacatenars exhibited columar hexagonal phase. p-Sub-stituted hexacatenar with n-dodecyloxy tails exhibited thermochromism, with the highly emissive Col h phase and non-emissive soft crystal phase. Three p-substituted compounds exhibited supergelation exclusively promoted by p-p interactions. Besides the capability to form self-standing, moldable gel, one of the compounds exhibited technologically important aggregation-induced blue light emission. The columnar order and emissive nature in the aggregated state makes these molecules promising for the application in emissive displays.

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Section: Resultsmentioning

confidence: 99%

Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism

et al. 2016

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“…[6b] 1,3,4-Oxadiazole derivatives, whicha re known for their electron-deficient and fluorescence nature, aref inding applications in OLEDs as electron transport and electroluminescent layers. [13] However,t here are no reports on thiophene-containing organogels, which are stabilized mainly by p-p interactions. [10] 1,3,4-Thiadiazole derivatives are less often reported, but they also exhibit promising thermal and photophysical behavior.…”

Section: Introductionmentioning

confidence: 99%

“…Recently,afew liquid crystalline polycatenars with 1,3,4-oxadiazole units have exhibitedg elation, whichi se xclusively supported by p-p interactions. [13] However,t here are no reports on thiophene-containing organogels, which are stabilized mainly by p-p interactions. Tailoring the molecular structure to obtain these long-range-ordered self-assembled structures is important,g iven their potentiala pplicationsi no ptoelectronic devices.…”

Section: Introductionmentioning

confidence: 99%

Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States

Pradhan

Mohanan

Nair

et al. 2016

Chemistry A European J

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Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole-based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole-based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin-film states. Two oxadiazole-based molecules and one thiadiazole-based molecule exhibited supergelation ability in hydrocarbon solvents, which is mainly supported by attractive π-π interactions. These gels showed aggregation-induced enhanced emission, which is of high technological importance for applications in solid-state emissive displays. X-ray diffraction studies of the xerogel fibers of oxadiazole-based polycatenars revealed a columnar rectangular organization, whereas a hexagonal columnar arrangement was observed for thiadiazole-based polycatenars. Rheological measurements carried out on the samples quantitatively confirmed the formation of gels and showed that these gels are mechanically robust. The impact of an atomic-scale difference (oxygen to sulfur, <2 % of the molecular weight) on the self-assembly and the macroscopic properties of those self-assembled structures are clearly visualized.

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“…[14d, e, 17] When placed under destructive strain,t he mechanical properties of gels are lost, and most do not regain their viscoelasticity after the cessation of the destructive strain (i.e.,t hey are not thixotropic); [18] SAFiNso fm ost known thixotropic gels are non-crystalline [19] or liquid-crystalline. [20] One of the very few examples of thixotropic molecular gels with crystalline SAFiNsisb ased on gels with the fatty acid derived gelator, N-(3-hydroxypropyl)dodecanamide, and toluene as the liquid. [21] (9Z)-Octadecenoic acid (oleic acid, OA), another naturally occurringf atty acid and am ajor component of canola oil, has been studied extensivelyb ecause of its importance in cell membranes.…”

Section: Introductionmentioning

confidence: 99%

Mechano‐Responsive, Thermo‐Reversible, Luminescent Organogels Derived from a Long‐Chained, Naturally Occurring Fatty Acid

Zhang

Weiss

2016

Chemistry A European J

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The gelating ability of an α-diketo derivative of oleic acid, 9,10-dioxooctadecanoic acid (DODA), is investigated. DODA can gelate aromatic liquids and many other organic liquids. By contrast, none of the liquids examined can be gelated by the methyl ester of DODA. DODA is a more efficient gelator than stearic acid and the monoketo derivative due to its more extensive intermolecular dipole-dipole interactions. Formation of organogels of DODA can be induced by both thermal and mechanical stimuli, during which the luminescent and mechanical properties can be modulated significantly. The emission from DODA in 1-octanol exhibits a large, reversible, hypsochromic shift (≈25 nm) between its thermally cycled gel and sol states. The emission changes have been exploited to probe the kinetics of the aggregation and deaggregation processes. DODA is the simplest gelator of which we are aware that exhibits a reversible shift in the emission. Although the self-assembled fibrillar networks of the DODA gels in 1-octanol, benzonitrile, or silicone oil are crystalline, isothermal mechanical cycling between the gel and the sol states is rapid and can be repeated several times (i.e., they are thixotropic). The single-crystal structure of DODA indicates that extended intermolecular dipole-dipole interactions are crucial to the thermal and mechanical formation of DODA gels and the consequential changes in emissive and mechanical properties. From analyses of structural information, gelator packing, and morphology differences, we hypothesize that the mechanical destruction and reformation of the gel networks involves interconversion between the 3D networks and 1D fiber bundles. The thermal processes allow the fibrillar 3D networks and their 0D components (i.e., isolated molecules or small aggregates of DODA) to be interconverted. These results describe a facile approach to the design of mechano-responsive, thermo-reversible gels with control over their emission wavelengths.

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Supergelation via Purely Aromatic π–π Driven Self-Assembly of Pseudodiscotic Oxadiazole Mesogens

Cited by 53 publications

References 70 publications

Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism

Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism

Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States

Mechano‐Responsive, Thermo‐Reversible, Luminescent Organogels Derived from a Long‐Chained, Naturally Occurring Fatty Acid

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