A new series of nematic and smectic liquid crystals with negative dielectric anisotropy: the effect of terminal chain substitution on thermal and electro-optical properties

作者：Jankowiak Aleksandra; Januszko Adam; Ringstrand Bryan; Kaszynski Piotr^*

来源：Liquid Crystals, 2008, 35(1): 65-77.

DOI：10.1080/02678290701744561

Two alkyl (1b and 1c) and four fluoroalkyl derivatives (1d-1f) of 4-arylbutyric acid (1c, 1d and 1e) and 4-arylbutanol (1b, 1f and 1g) [aryl=2',3'-difluoro-4'-(2-(E-4-pentylcyclohexyl)ethyl)-biphenyl-1-yl] were prepared and investigated in the pure form as nematic materials (1b and 1c) and as additives to a ferroelectric liquid crystal (FLC) host (1d-1f). A comparison of 1b and 1c with the decyl analogue 1a demonstrates the effect of terminal chain modification on thermal and electro-optical properties. The substitution of the -CH2O- (1b) or -COO- (1c) for -CH2CH2- in 1a destabilized the N and SmA phases or completely eliminated the smectic behaviour (1c). Dielectric analysis revealed that the chain modification increased the negative Delta epsilon, reduced elastic constant K-11 and moderately decreased rotational viscosity 1. The temperature dependence of the key electro-optical parameters was analysed for ester 2, the methyl analogue of 1c, which exhibits a 45K wide N phase. All four fluoroalkyl derivatives 1d-1f showed enantiotropic SmA phases and 1e also exhibited a monotropic SmC phase. Solutions of 1d-1f in a FLC host (0.2mmolg(-1)) increased the tilt angle Theta (up to 45 degrees for 1g), reduced rotational viscosity gamma(1) and the risetime tau. The most dramatic changes were observed for 1g, which contains 15 fluorine atoms.

• 出版日期2008