Mesomorphic properties of fluorinated cholesteric three-arm liquid crystals based on chenodeoxycholic acid

Abstract

ABSTRACT Five non-symmetric three-arm liquid crystals (LCs) based on chenodeoxycholic acid (CDCA), termed as EFSD, EFSL, EFXD, EFXL and EFDZ, were synthesised. EF, which is a chiral smectic A (SmA*) LC, was synthesised by using CDCA as the chiral core and introducing fluorinated LC arm, 4ʹ-((10-chloro-10-oxodecanoyl)oxy)-[1,1ʹ- biphenyl]-4-yl 4-(trifluoromethyl)benzoate, into the hydroxyl of CDCA. The third side arm with different rigidity and the length of the terminal chain was introduced into the carboxyl group of CDCA to prepare the non-symmetric three-arm LCs. The results indicate that the proper increase of the third side arm’s rigidity can stabilise the LC phases and widen LC ranges. In addition, the structure of the third side arm also had an influence on the LC phase type. EFSD, EFXD, EFXL and EFDZ display cholesteric (Ch) phases, while EFSL exhibits chiral smectic C (SmC*) phase. The longer alkyl terminal chain of the third side arm can lead to the appearance of lamellar phase. For this type LCs, it is beneficial to the formation of Ch phase LCs to adopt short alkyl terminal chain. That EFDZ displays Ch phase may be due to the increase of molecular biaxiality of EFDZ due to the biaxiality of cholesterol. 궜