Cholesteric Structure of Lyotropic Poly (γ-benzyl L-glutamate) Liquid Crystals

Toriumi, Hirokazu; Yahagi, Kazukyuki; Uematsu, Ichitaro; Uematsu, Yoshiko

doi:10.1080/15421408308084262

Cited by 28 publications

(18 citation statements)

References 19 publications

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“…A precipitate slowly forms on standing at temperatures below the transition shown in Figure , providing clear evidence of aggregation. It may be significant that within the wavelength range studied, the CD spectrum below T OPT is identical to that observed for the cholesteric liquid crystal formed in solutions of PBG in good solvents at higher concentration . The similarity of the CD spectrum below T OPT with that of the cholesteric liquid crystal is consistent with the essentially parallel organization determined by the light scattering results for PBPMG.…”

Section: Discussionsupporting

confidence: 72%

Intermolecular Association and Supramolecular Organization in Dilute Solution. 2. Light Scattering and Optical Activity of Poly(p-biphenylylmethyl l-glutamate)

Yue

Berry

Green³

1996

Macromolecules

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Static and dynamic light scattering measurements are reported on dilute solutions of poly(p-biphenylylmethyl l-glutamate), PBPMG, in the helicogenic solvent THF, over a temperature range encompassing an observed reversible transition in the chiral optical properties of these solutions. The results confirm the expected helical conformation for this polypeptide, as well as complete dissolution of the polymer at temperatures above the transition temperature. Association is observed at lower temperatures, with the chains in an ordered parallel array within the aggregates. The association occurs with increasingly poor solvent conditions as the temperature is decreased, with the degree of association in the aggregate increasing concurrently with the change in the optical rotation and circular dichroism (CD) spectrum. It is concluded that the intermolecular association of the chains in the parallel array alters the chiral electronic environment of the biphenyl group, without a conformation change in that chromophore, resulting in the observed transition in the optical rotation and the CD spectrum. Unlike the behavior reported for certain other aggregated systems, the optical transition observed with solutions of PBPMG does not involve the initial formation of a disordered aggregate, which orders itself on reduced solvent quality or temperature, but rather a spontaneous association, such as expected on crossing a phase boundary, with a concurrent optical transition.

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Section: Discussionsupporting

confidence: 72%

Intermolecular Association and Supramolecular Organization in Dilute Solution. 2. Light Scattering and Optical Activity of Poly(p-biphenylylmethyl l-glutamate)

Yue

Berry

Green³

1996

Macromolecules

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“…Concentrated solutions of DNA 14,15 form both left-and right-handed cholesterics with different pitch versus temperature trends depending on the sequence of oligomers 16 . Spontaneous helix inversions upon change of temperature were observed in thermotropic systems of polypeptides 17 and cellulose 18 , and inversions upon changing the solvent conditions were reported for lyotropic systems poly-benzyl-L-glutamate 19 indicating that the nematic twist is governed by a subtle balance of forces whose exact origin remains partly obscure.…”

Section: Introductionmentioning

confidence: 99%

Simulating the pitch sensitivity of twisted nematics of patchy rods

Růžička

Wensink

2016

Soft Matter

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Stiff, elongated biomolecules such as filamentous viruses, DNA or cellulose nanocrystals are known to form liquid crystals often exhibiting a helical supramolecular organization. Little is known about the microscopic origin, size and handedness of the helical pitch in these, so-called cholesteric phases. Experimental observations in chiral lyotropics suggest that long-ranged chiral forces of electrostatic origin acting between the mesogens are responsible for such organization. Using large-scale computer simulation we study the sensitivity of the pitch imparted by soft microscopic helices and confirm that the helical sense is sensitive to a change of packing fraction, magnitude of the molecular pitch and amplitude of the chiral interactions. In particular, we find evidence that the cholesteric helix sense may change spontaneously upon variation of particle density, at fixed molecular chirality. These pitch inversions have been reported in recent theoretical studies but simulation evidence remains elusive. We rationalize these sudden changes in the supramolecular helical symmetry on the basis of detailed measurements of the mean-torque generated by the twisting of the helices. The simulation methodology employed does not require confining the twisted nematic in a slab geometry and allows for a simultaneous measurement of the pitch and the twist elastic constant. We find that the twist elastic constant increases almost linearly with density suggesting that twisted nematic shows no signs of anomalous stiffening due to pre-smectic fluctuations at higher packing fraction.

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“…The pitch lengths of lyotropic chiral nematic LCs are sensitive to many factors, such as ionic strength, [ 45,46 ] temperature, [ 47 ] solvent dielectric properties, [ 48 ] concentration [ 49 ] and the presence of dopants. [ 50 ] Since the grating periodicity d is equal to half of the helical pitch in the CPGH, the grating parameters can be readily modulated by changing these conditions.…”

Section: Methodsmentioning

confidence: 99%

Tunable Diffraction Gratings from Biosourced Lyotropic Liquid Crystals

et al. 2020

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Diffraction gratings are important for modern optical components, such as optical multiplexers and signal processors. Although liquid crystal (LC) gratings based on thermotropic LCs have been extensively explored, they often require expensive molecules and complicated manufacturing processes. Lyotropic LCs, which can be broadly obtained from both synthetic and natural sources, have not yet been applied in optical gratings. Herein, a facile grating fabrication method using a biosourced lyotropic LC formed by cellulose nanocrystals (CNCs), a material extracted from plants, is reported. Hydrogel sheets with vertically aligned uniform periodic structures are obtained by fixing the highly oriented chiral nematic LC of CNCs in polymer networks under the cooperative effects of gravity on phase separation and a magnetic field on LC orientation. The hydrogel generates up to sixth‐order diffraction spots and shows linear polarization selectivity, with tunable grating periodicity controlled through LC concentration regulation. This synthesis strategy can be broadly applied to various grating materials and opens up a new area of optical materials from lyotropic LCs.

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Cholesteric Structure of Lyotropic Poly (γ-benzyl L-glutamate) Liquid Crystals

Cited by 28 publications

References 19 publications

Intermolecular Association and Supramolecular Organization in Dilute Solution. 2. Light Scattering and Optical Activity of Poly(p-biphenylylmethyl l-glutamate)

Intermolecular Association and Supramolecular Organization in Dilute Solution. 2. Light Scattering and Optical Activity of Poly(p-biphenylylmethyl l-glutamate)

Simulating the pitch sensitivity of twisted nematics of patchy rods

Tunable Diffraction Gratings from Biosourced Lyotropic Liquid Crystals

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