Ferroelectric liquid crystal polymers

Abstract

The ferroelectricity of liquid crystal polymers can be utilized in electro-optic display devices. Liquid crystal polymers (LCP´s) unite the properties of liquid crystals and of polymers, where the mesophase can be frozen in the polymer glass. The mesophase responsible for ferroelectricity is the chiral smectic C$^*$ phase (SmC$^*$), which can be generated by mesogen side groups bearing chiral carbon atoms. This also means that ferroelectric liquid crystal polymers are side chain polymers with the mesogen groups in the side chain. According to the main chain, polysiloxanes, polyacrylates, polyethers and polyvinylethers are the most important groups of FLCP´s. Our work can be divided into two main parts: One is the synthesis and characterization of the mesogen side groups, the other is the preparation of the corresponding polymer via polymerization or polymeranalog reaction. As the polymer main chain, polysiloxanes and polyacrylates were selected for the syntheses. For polysiloxanes the following mesogen groups were synthesized: Br-(CH2)10-COO-C6H4-COO-C6H4-COO-CH2-C*H(CH3)-C2H5 (S)-4´-(2-methyl-butyloxicarbonyl)-phenyl-4-[11-bromo-undecanoyloxi]-benzoate The polymer can be prepared by the addition of poly(methyl-hydrogen-siloxane) to the double bond of the mesogen monomer: For polyacrylates the following mesogen side group was prepared: CH2=CH-(CH2)n-O-C6H4-COO-C6H4-O-CH2-C*H(CH3)-C2H5 n = 8 (S)-4`-(2-methyl-butyloxy)-phenyl-4-(9-decenyloxy)-benzoate n = 9 (S)-4`-(2-methyl-butyloxy)-phenyl-4-(10-undecenyloxy)-benzoate The mesogen side group can be transferred to the polymer acrylate via a polymeranalog reaction. The synthesis of the mesogen side group for polysiloxanes is described in detail.