The Origin of High Optical Tilt in a Homologous Series of Fluorinated Antiferroelectric Liquid Crystals

The compounds from the fluorinated nF6B (n = 1,2,3,4,5,6,7) homologous series were investigated by means of optical, electrooptical, refractometrical, dielectric, densytometric, X-ray and IR spectroscopy methods. For some compounds being a subject of investigations a computer simulation of molecular properties were done. In our opinion high value of optical tilt Θ_o angle in comparison with a tilt angle obtained from X-ray measurements can be interpreted in terms of de Vries model of SmA* phases as well as of dimers creation process.

Keywords:

• antiferroelectric liquid crystals
• ferroelectric liquid crystals
• helical pitch
• layer spacing
• orthoconic antiferroelectric liquid crystals
• refractive indices
• spontaneous polarisation
• tilt angle

Acknowledgments

This work was supported by the Polish Ministry of Scientific Research and Information Technology in years 2003–2006 (grant No. 0 T00C 006 25).

Notes

l - Calculated Optimum Molecular Length, l_m - Calculated Length of Fully Extended Molecule, L₁ - Calculated Total Length of Dimer 1, L₂ - Calculated Total Length of Dimer 2, μ - Calculated Total Dipole Moment of Single Isolated Molecule, μ₁ - Calculated Total Dipole Moment of Virtual Dimer 1, μ₂ - Calculated Total Dipole Moment of Virtual Dimer 2, d - Measured by SAXS Layer Spacing of the SmC* Phase at T – T_AC = 60°C, d_A-Measured by SAXS Layer Spacing of the SmA* Phase at T – T_AC = + 2°C, L_A - Estimated Average Length of Objects Which Build up the SmA* Phase, L - Estimated Average Length of Objects Which Build up the SmC* Phase at T – T_AC = − 60°C, Θ_A = acos(d_A/L_A) - Calculated Tilt Angle in the de Vrise SmA* Phase, Θ = acos (d/L) - Calculated Tilt Angle in the de SmC* Phase at T – T_AC = 60°C.