Mesomorphic properties of chiral nematic star-shaped liquid crystals containing melitose as cores

Three star-shaped compounds (SSCs, c1-c3), are synthesized by using melitose as the chiral core and monacid (b1, b2 and b3) as side arms, respectively. The side arms (b1, b2 and b3), in which terminal chains are different, are introduced into the hydroxyl groups of melitose by esterification. respectively. The chemical structures of c1-c3 are confirmed by FT-IR and H-1 NMR. The roles played by the chiral core and the side arms in the mesomorphic properties of the SSCs are studied. b1 is not a liquid crystal (LC), while b2 and b3 are nematic LCs. c1 is not a LC, while c2 and c3 are star-shaped LCs (SSLCs) and exhibit fingerprint texture of chiral nematic. c1, c2 and c3 are all levo-SSCs, which are different from their parent cores. The absolute value of their specific rotation increases with the increase of the terminal chain length of the side arms. The melting temperature of SSCs decreases with the increase of the terminal chain length of the side arms. For c2-c3, their mesomorphic region increases with the increase of the terminal chain length of the side arms. The results suggest that the LC properties of the side arms play an important role in inducing LC properties of the SSCs and the chiral core induces the chiral nematic of SSLCs, which contain the nematic LCs as the side arms. (C) 2009 Elsevier B.V. All rights reserved.