An H‐Bonded Main‐Chain Liquid‐Crystalline Polymer Obtained by In Situ Photochemical Conversion from an H‐Bonded LC Dimer

Kihara, Hideyuki; Tamaoki, Nobuyuki

doi:10.1002/macp.200800063

Cited by 5 publications

(2 citation statements)

References 54 publications

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“…A decrease in the trans ‐vinylene C‐H out‐of‐plane deformation (Figure S4) is diagnostic of a [2+2] cycloaddition reaction of the alkene 15. 19 This indicated that 2‐NA formed a cyclobutane structure in the gel. Meanwhile, the appearance of a bending vibration of the saturated C‐H of the cyclobutane at $\tilde \nu $ =1441 cm −1 in the spectrum of the 2‐NA precipitate (Figure S5) verified the topochemical reaction 20.…”

Section: Resultsmentioning

confidence: 94%

Organogelation‐Controlled Topochemical [2+2] Cycloaddition and Morphological Changes: From Nanofiber to Peculiar Coaxial Hollow Toruloid‐Like Nanostructures

Wang

Duan

Liu

2013

Chemistry A European J

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Novel amphiphilic molecules composed of naphthylacryl and L-glutamide moieties (1-NA and 2-NA) have been designed and their organogel formation in various organic solvents as well as their self-assembled nanostructures have been investigated. Both compounds formed organogels in many organic solvents, ranging from nonpolar to polar, and self-assembled into essentially nanofiber structures, although some twist or belt structures could be observed in certain solvents. A gel of compound 2-NA in ethanol initially self-assembled into nanofibers and then these were transformed into a family of coaxial hollow toruloid-like (CHTL) nanostructures under irradiation, in which various toroids and disks of different sizes were stacked coaxially. We have established that a topochemical [2+2] cycloaddition in the organogel triggers this transformation. When the gel was fabricated into xerogels in which no ethanol remained, such morphological changes could not happen. This might be the first report of an organogel, in which both organized nanofibers and solvent coexist, controlling a topochemical reaction as well as the self-assembled nanostructures formed. Due to the formation of the toruloid-like nanostructures, the gel collapsed to a precipitate. However, upon heating this precipitate with ethanol, it redissolved and then formed a gel and self-assembled into nanofibers once more. Thus, a reversible morphological transformation between nanofibers and an unprecedented series of toruloid-like nanostructures can be induced by alternately heating and irradiating the gel.

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Section: Resultsmentioning

confidence: 94%

Organogelation‐Controlled Topochemical [2+2] Cycloaddition and Morphological Changes: From Nanofiber to Peculiar Coaxial Hollow Toruloid‐Like Nanostructures

Wang

Duan

Liu

2013

Chemistry A European J

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“…Moreover, the intensities of the vinylene C]C stretching vibration band at 1636 cm À1 is significantly lowered, and the ]C-H stretching and deformation vibration bands at 3040 cm À1 and 970 cm À1 disappear after 4 h irradiation. [36][37][38][39][40][41][42] These are powerful proofs for the loss of the vinylene C]C bond due to photodimerization. Meanwhile, the appearance of the stretching and bending vibration of saturated C-H of the cyclobutane at 2899 and 1343 cm À1 , 37 respectively, after UV irradiation, unambiguously confirms the occurrence of the photodimerization in the tubular membranes formed by SHHC molecules.…”

Section: Resultsmentioning

confidence: 99%

Unprecedented parallel packing of unsymmetrical bolaamphiphiles driven by π–π stacking of cinnamoyl groups

Zhao

Yan

et al. 2010

Soft Matter

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The self-assembly and molecular packing mode of a novel, unsymmetrical bolaamphiphile, sodium 4-(6-hydroxyhexyloxy) cinnamate (SHHC) was studied. Tube-like structures were obtained in SHHC aqueous solution at pH 9.2. Upon UV irradiation, the SHHC molecules in the system were found to undergo four-center-type photocyclodimerization and photoisomerization. The combination of IR, XRD and Zeta potential results suggested the formation of a tail-to-tail type bilayer membrane structure: the SHHC molecules stretched upright with the cinnamate headgroups toward the outside in each layer, whereas the tail OH groups of two layers remained inside and formed interlayer hydrogen bonds. This parallel packing mode of SHHC molecules in the membrane was also confirmed by the pHinduced self-assembly transition. With increasing pH from 9.2 to 12.0, the low-curvatured tubes transformed into spherical vesicles, which was in line with the increased outer leaflet head group area as increasing pH. Our results demonstrated that upon careful molecular design, the orientation of unsymmetrical bolaamphiphiles can be controlled; p-p interactions between cinnamoyl groups were found to be strong enough to drive the formation of well-oriented molecular assemblies.

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Vicinal Solvent Effect on Supramolecular Gelation: Alcohol Controlled Topochemical Reaction and the Toruloid Nanostructure

Wang

Liu

2014

Chemistry A European J

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Although solvent is the major component of the gel, it still remains unclear how the solvent molecules take part in the formation of the gel nanostructures in many gels. In this study it was observed that the vicinal effect on gel formation as well as their nanostructures, that is, the vicinal solvent molecules to the gelator, determine the molecular packing and their subsequent structures and properties. A naphthylacryl-conjugated L-glutamide gelator was found to form organogels in various solvents and nanofiber structures. While the nanofibers from other solvents could not show any further reaction, the gel from the alcohol could undergo topochemical [2+2] cycloaddition under photoirradiation and resulted in toruloid nanostructures. Various pure alcohol solvents from methanol to pentanol were found to show a similar property. Interestingly, switching from a single alcohol solvent to mixed solvents of alcohol with miscible or immiscible non-alcohol solvents could still cause the same change, showing the vicinal effect of alcohol on controlling the molecular packing as well as the structural transformation. More interestingly, when nanofiber xerogel, obtained from non-alcohol solvents, was exposed to alcohol vapor, the nanofiber was transferred into nanotoruloid. These results provide a new insight into the gelator-solvent interaction in soft gels.

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An H‐Bonded Main‐Chain Liquid‐Crystalline Polymer Obtained by In Situ Photochemical Conversion from an H‐Bonded LC Dimer

Cited by 5 publications

References 54 publications

Organogelation‐Controlled Topochemical [2+2] Cycloaddition and Morphological Changes: From Nanofiber to Peculiar Coaxial Hollow Toruloid‐Like Nanostructures

Organogelation‐Controlled Topochemical [2+2] Cycloaddition and Morphological Changes: From Nanofiber to Peculiar Coaxial Hollow Toruloid‐Like Nanostructures

Unprecedented parallel packing of unsymmetrical bolaamphiphiles driven by π–π stacking of cinnamoyl groups

Vicinal Solvent Effect on Supramolecular Gelation: Alcohol Controlled Topochemical Reaction and the Toruloid Nanostructure

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