Novel high birefringence dibenzothiophenylacetylene liquid crystals

Abstract

We have designed, synthesized and evaluated dibenzothiophenylacetylene homologues as new heterocyclic molecules which were expected to have high Da values and short wavelength UV absorption spectra. The dibenzothiophenyl acetylene homologues exhibited wide nematic phase ranges and had very high extrapolated Dn of over 0.6 and directly measured values of 0.5. The compounds with two dibenzothiophenyl rings were colourless, so that we have succeeded in obtaining colourless super-high Dn liquid crystals. We have also analysed the contribution of the transition band to the refractive indices and the birefringence. From the analysis, the main origins of Dn for compounds 1 and 2 are lower MOs than the HOMO and this results in the compatibility of large Dn and lack of colour. The dibenzothiophenylacetylene compounds behaved according to our design expectations.

High Birefringence Liquid Crystals

“…Other heterocyclic derivatives with benzotiazole and dibenzothiophene moiety were prepared by Sekine et al [125,126], and they obtained compounds reaching Δn = 0.6, but which have unfavorably high melting points and additionally, the absorption of light is observed at 300-400 nm. …”

“…It is the cyano derivative, so the isothiocyanato analogue should have an even higher Δn value. Napthalene derivatives such as compound 123 have only nematic phase in the presence of an ethyl lateral group [125,126].…”

Spontaneous Formation of Inorganic Paper‐Like Materials

“…The electro-optic measurements were made using He±Ne laser light (632.8 nm) with crossed polarizers at room temperature. Next, another nematic LC (PA1109) [17] was used in polarized reflectance measurements of a LC-filled Fabry±Perot cavity with PC films as a function of the amplitude of the applied rectangular voltage (f = 1 kHz). [1±7] Formation of ordered macroscopic, mesoscopic, and microscopic materials such as inorganic thin films and membranes has been an important goal, especially when specific physical properties such as porosity, permeability, and conductivity are of interest.…”

High Figure-of-Merit Laterally Fluorinated Biphenyltolane-Isothiocyanates

“…Several high birefringence molecular structures, such as diphenyldiacetylene [4,5], bistolane [6,7], naphthalene tolanes [8], and thiophenyl-diacetylene [9][10][11] have been studied. Recently some of biphenyl-tolane compounds were synthesized and their properties were investigated [12][13][14].…”