Add time:08/09/2019         Source:sciencedirect.com

By the method of polarizing microscopy, a chiral nematic phase formation of the 4-(n)alkoxy-4′-cyanobiphenyls (n = 3,4,5,6,7,8) nematic mixtures (CB6) was observed under the influence of 1R(+)1′,7′,7′-trimethylbicyclo[2.2.1]heptane[2′,3′-b]-2,3-dicyanopyrazine (R(+) СDCP). The values of clearance temperature and pitch were measured and helical twisting power (β) was calculated. The degree of racemic mixture (±)CDCP and chiral R(+)СDCP destabilizing action on liquid crystalline phase was determined. As the result of birefringence and 1H NMR splitting analysis, optical properties in nematic LC and quasinematic layers of chiral phase were established to depend on orientational order parameter.On the base of binary systems CB6 + R(+)СDCP and CD6 +(±)CDCP permittivity and the dielectric anisotropy of achiral mixture were found to slightly depend on dopant concentration whereas in the case of helical mesophase the essential decrease in anisotropy with R(+)СDCP content rise was observed. As the result of Kirkwood's factor analysis and quantum-chemical calculation the polar dopant was shown to influence on LC associative state due to dipole-dipole interaction of R(+)СDCP with LC cyano group.

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