1 February 1998 Optical anisotropy and orientational elastic constants of polymer high-temperature and re-entrant nematics
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Abstract
Orientational elastic deformations of polymer high temperature and reentrant nematics in a magnetic field were studied using the method of Freedericksz transitions. Experiments were performed on a series of fractions of a comb-like polymer. The temperature dependences of orientational elastic constants K1 and K3 in the nematic and reentrant nematic phases and birefringence (Delta) n and, correspondingly, the orientational order parameters S do not undergo a pronounced jump. The study of mechanical equilibrium characteristics did not reveal any differences in the behavior of high temperature and reentrant nematic phases of the polymer. For the lowest molecular weight fraction, an anomalous 'bell-shaped' temperature dependence of the bend constant K3 was found. This dependence can be explained by the formation of small domains with smectic ordering in the nematic phase. In the molecular weight range investigated, both optical anisotropy and equilibrium mechanical characteristics are independent of M.
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Alexander P. Filippov, Alexander P. Filippov, L. N. Andreeva, L. N. Andreeva, E. B. Barmatov, E. B. Barmatov, Valery P. Shibaev, Valery P. Shibaev, } "Optical anisotropy and orientational elastic constants of polymer high-temperature and re-entrant nematics", Proc. SPIE 3318, Liquid Crystals: Physics, Technology, and Applications, (1 February 1998); doi: 10.1117/12.300004; https://doi.org/10.1117/12.300004
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