Chiral Molecular Self‐Assembly

Spector, Mark S.; Selinger, Jonathan V.; Schnur, Joel M.

doi:10.1002/0471471895.ch5

Cited by 37 publications

(9 citation statements)

References 170 publications

(272 reference statements)

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“…In general, chiral molecules do not pack parallel to their neighbors but rather pack at a slight angle with respect to their neighbors which can arise from repulsive and/or attractive interactions leading to a twist in the orientation of the molecules. 102 In the literature, fibers with helical twists are reported for steroid based systems 102 and esters of arjunolic acid (another type of pentacyclic triterpenoid). 103 When we look at the structures of 2 and 3, besides having many chiral centers, they are amphiphilic in nature.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Chiral self-assembly can be expressed considering the packing pattern of chiral molecules as well. In general, chiral molecules do not pack parallel to their neighbors but rather pack at a slight angle with respect to their neighbors which can arise from repulsive and/or attractive interactions leading to a twist in the orientation of the molecules . In the literature, fibers with helical twists are reported for steroid based systems and esters of arjunolic acid (another type of pentacyclic triterpenoid) .…”

Section: Resultsmentioning

confidence: 99%

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Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates

et al. 2021

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Natural and abundant plant triterpenoids are attractive starting materials for the synthesis of conformationally rigid and chiral building blocks for functional soft materials. Here, we report the rational design of three oleanolic acid–triazole–spermine conjugates, containing either one or two spermine units in the target molecules, using the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The resulting amphiphile-like molecules 2 and 3, bearing just one spermine unit in the respective molecules, self-assemble into highly entangled fibrous networks leading to gelation at a concentration as low as 0.5% in alcoholic solvents. Using step-strain rheological measurements, we show rapid self-recovery (up to 96% of the initial storage modulus) and sol ⇔ gel transition under several cycles. Interestingly, rheological flow curves reveal the thixotropic behavior of the gels. To the best of our knowledge, this kind of behavior was not shown in the literature before, neither for a triterpenoid nor for its derivatives. Conjugate 4, having a bolaamphiphile-like structure, was found to be a nongelator. Our results indicate that the position and number of spermine units alter the gelation properties, gel strength, and their self-assembly behavior. Preliminary cytotoxicity studies of the target compounds 2–4 in four human cancer cell lines suggest that the position and number of spermine units affect the biological activity. Our results also encourage exploring other triterpenoids and their derivatives as sustainable, renewable, and biologically active building blocks for multifunctional soft organic nanomaterials.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates

et al. 2021

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“…3 It has been shown that a number of synthetic lipids with modified head groups or acyl chains are able to self-assemble into tubule structures in solutions. [4][5] The diameters of self-assembled lipid tubules span the range between 10 nm and 2.0 µm depending on the nature of the lipid molecules and the condition under which self-assembly occurs.…”

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confidence: 99%

Buckling of Lipid Tubules in Shrinking Liquid Droplets

Zhao

Fang

2007

Nano Lett.

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Self-assembled hollow lipid tubules are interesting and potentially useful supramolecular structures. Here, we study the deformation of lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) trapped inside liquid droplets on glass substrates. The interface tension of the shrinking liquid droplets exerts a compression force on the ends of the trapped lipid tubules, and causes them to buckle. This provides a method to measure their mechanical properties. The Young's modulus of the DC8,9PC lipid tubules is estimated to approximately 1.07 GPa. As the strain energy of the buckled tubules builds up, they poke through the interface of shrinking liquid droplets and then adhere onto glass substrates to form looplike shapes.

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“…Lipid tubules. Many types of amphiphilic molecules self-assemble in aqueous solution into aggregates with chiral structures, as reviewed in Reference (53). In some cases, these aggregates are twisted ribbons with negative Gaussian curvature, similar to the helical nanofilaments discussed above.…”

Section: Further Constraints If Layers Are Solidmentioning

confidence: 96%

Director Deformations, Geometric Frustration, and Modulated Phases in Liquid Crystals

Selinger¹

2021

Preprint

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This article analyzes modulated phases in liquid crystals, from the longestablished cholesteric and blue phases to the recently discovered twistbend, splay-bend, and splay nematic phases, as well as the twist-grainboundary (TGB) and helical nanofilament variations on smectic phases. The analysis uses the concept of four fundamental modes of director deformation: twist, bend, splay, and a fourth mode related to saddle-splay. Each mode is coupled to a specific type of molecular order: chirality, polarization perpendicular and parallel to the director, and octupolar order. When the liquid crystal develops one type of spontaneous order, the ideal local structure becomes nonuniform, with the corresponding director deformation. In general, the ideal local structure is frustrated; it cannot fill space. As a result, the liquid crystal must form a complex global phase, which may have a combination of deformation modes, and may have a periodic array of defects. Thus, the concept of an ideal local structure under geometric frustration provides a unified framework to understand the wide variety of modulated phases.

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Chiral Molecular Self‐Assembly

Cited by 37 publications

References 170 publications

Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates

Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates

Buckling of Lipid Tubules in Shrinking Liquid Droplets

Director Deformations, Geometric Frustration, and Modulated Phases in Liquid Crystals

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