Ferroelectric liquid crystals with axially chiral 2,2′-spirobiindan-1,1′-dione cores

Abstract

The axially chiral mesogens 5-alkoxy-5 -[(4-alkoxybenzoyl)oxy]-2,2 -spirobiindan-1,1 -dione (QL7-n) were synthesised as racemic mixtures and resolved as single enantiomers by preparative chiral phase HPLC. The shorter homologues (R)-QL7-8 and QL7-9 form enantiotropic N * and SmC * phases, whereas the longer homologues (R)-QL7-10 and QL7-12 form an enantiotropic SmC * phase only. Texture analysis showed that the helical pitch of the N * phase is below the wavelength range of visible light; a helical pitch of 187 nm was measured at T -T NI = -5 K by selective reflection using enantiomerically enriched mixtures of (R)-and (S)-QL7-8 (0.35 ≤ ee ≤ 0.80). Spontaneous polarisations were measured as a function of temperature in the SmC * phase by the triangular wave method. P S values at saturation range from 102 nC cm -2 for (R)-QL7-8 to 120 nC cm −2 for (R)-QL7-9, which are up to three times greater than the highest polarisation previously reported for an axially chiral SmC * mesogen. Optical tilt angles θ were measured as a function of temperature and showed a sharp rise consistent with first-order N * -SmC * or I-SmC * transitions, with values at saturation ranging from 42 to 44 • .

The 2013 Luckhurst-Samulski Prize

“…The fourth of these papers by Cui and Lemieux entitled Ferroelectric liquid crystals with axially chiral 2,2′-spirobiindan-1,1′-dione cores [20] describes the synthesis and characterisation of a new homologous series of axially chiral materials which all exhibit the ferroelectric smectic C phase. The values of the spontaneous polarisation measured in these phases are considerably higher than those previously reported in the literature for axially chiral materials.…”