End functionalised liquid crystalline bent-core molecules and first DAB derived dendrimers with banana shaped mesogenic units

Abstract

New series of non-symmetric bent-core compounds with a terminal carboxylic function as well as its benzyl esters and pentafluorophenyl esters have been synthesised. For most pentafluorophenylesters and for a benzylester with fluorine atoms in the ortho positions to the alkoxy chain different types of columnar ribbon phases (Col_rP_A and Col_obP_A) and a polar smectic SmCP_A phase have been observed. Both the columnar and the smectic phases show antiferroelectric switching behaviour. Based on these functionalised banana-shaped molecules the first example of an amphiphilic bent-core molecule with a terminal 1-acylaminopropane-2,3-diol unit and DAB derived dendrimers of the first as well as the second generation have been synthesised and their physical properties have been investigated. Neither the diol-terminated bent-core molecule nor the dendrimers show any electrooptical response. Dendrimers with long aliphatic chains as well as the amphiphile form non-polar bilayer smectic phases, whereas dendrimers with shorter chains organise into a mesophase with a 2D lattice (Col). It seems that hydrogen bonding at the periphery of the bent-core units is unfavourable for the formation of polar smectic phases.