Abstract
We investigated the twisted structure in the cholesteric liquid crystals in which the directors n (parallel to axes of α-helical molecules of polypeptides) are helicoidally twisted about the helical axis. We propose here that this twisting occurs, in general, nonlinearly or inhomogeneously with displacement along the helical axis for the poly(γ-benzyl L-gultamate) systems studied in this work, in contrast to a picture of ‘linear twisting’ appearing in earlier literature on the cholesteric liquid crystals. The inhomogeneous twisting in the cholesterics is exhibited most spectacularly in the multiple-order scattering maxima of a laser-light. The deviation from the homogeneous twisting was studied as a function of cell thickness, solvent, polymer concentration, temperature, and aging; the results indicate that the inhomogeneous twisting of the directors is a general phenomenon in the lyotropic liquid crystal system studied in this work. We present a theory for elastic light scattering from the cholesteric mesophase having inhomogeneously twisted structure.
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References
T. Hashimoto, S. Ebisu, and H. Kawai, J. Polym. Sci., Polym. Lett. Ed., 18, 569 (1980).
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see for example, P.G. de Gennes, “The Physics of Liquid Crystals,” Clarendon Press, Oxford, 1974.
The concentration was specified by wt% which is a weight of solute divided by a weight of solution.
It should be noted that if the macroscopic orientation of the cholesteric domains exists, the pattern should be distorted also by the birefringence of the medium.8,9
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This is because the HV pattern is nearly identical to the VH pattern.
It is conceivable that the orientation of the directors has spatial fluctuations with respect to the cholesteric axis z. This fluctuations, however, give only a minor effect on our conclusion, unless the fluctuations occur periodically with z. Such special fluctuations are, of course, highly improbable, but the fluctuations should be more or less random. This random fluctuations generally broaden the line profiles of the multiple-order scattering maxima.
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Hashimoto, T., Inaba, N., Ebisu, S. et al. Supramolecular Structure of Polypeptides in Concentrated Solutions and Films. III. Inhomogeneous Twisting of Cholesteric Mesophase as Clarified from Multiple-Order Light-Scattering Maxima. Polym J 13, 897–910 (1981). https://doi.org/10.1295/polymj.13.897
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DOI: https://doi.org/10.1295/polymj.13.897
