engleski

Effect of Chirality in Polar Smectic Liquid Crystals

In this contribution, a detail analysis of structures and dynamical properties of chiral polar ferroelectric and achiral polar antiferrroelectric systems is presented. The analysis of relaxation modes in the ferroelectric SmC* phase has shown a non-linear temperature dependence of tilt and polar modes. Both type of modes change nature from tilt to polar and vice versa indicating that regularly used relation between the frequency and the amplitude of a relaxation mode in dielectric measurements is not correct. The analysis of the ferroelectric smectic system behaviour in weak alternating electric field lead to a theoretical prediction of modes polarity and their dependence on temperature. The analysis of theoretical models of pure and chirally doped antiferroelectric B2 subphases in bent-core systems confirmed that the chiral dopant induces tilt in the non-tilted phase and modifies tilts in the tilted phases, as was predicted by the chiroclinic effect. It was found that the dopant influences the stability ranges and the order of the transition between the chiral phases as well. The order of the phase transition changes from a continuous for weak effects of chiral doping to discontinuous for strong effects. Also, in this doped system the two phases with equal symmetries exist, which continuously transform one to another upon temperature changes. The analysis of dynamical properties allowed for development of the criterion which determines the temperature ranges of the two phases. The complete phase diagram of the doped system and theoretical predictions for potential experimental verification are the result of this work. The methods that lead to these findings, which could be used for the analysis of other similar soft matter systems, are presented in the contribution, as well.

(Anti)ferroelectric phases ; Bent-shaped molecules ; Chiral dopant ; Polar ; Smectic

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