Advanced Functional Materials
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Inside Front Cover: Observation of a Chiral Smectic Phase in Azobenzene-Linked Bolaamphiphiles Containing Free Sugars (Adv. Funct. Mater. 10/2005)
A chiral liquid-crystalline phase is reported for the first time in sugar-based mesogens containing free hydroxyl groups by Jayaraman, Das, and co-workers. Earlier reports have shown that hydrogen-bonding networks between hydroxyl groups in mesogenic sugars usually result in the manifestation of achiral smectic and columnar phases. The results reported on p. 1579 indicate that the manifestation of smectic C* phases in sugar-based bolaamphiphiles depends critically on the length of the methylene spacers and the presence of the azobenzene chromophore.
Amphiphilic sugars exhibit both lyotropic and thermotropic liquid-crystalline behavior. Interestingly, in spite of the abundance of chiral centers in amphiphilic sugars, their liquid-crystalline phases do not exhibit macroscopic chirality. Herein, we report on the first observation of macroscopic chirality in sugar-based bolaamphiphiles containing free hydroxyl groups. The manifestation of the chiral smectic C* phase in these bolaamphiphiles has been observed to be critically dependent on the presence of the azobenzene moiety and the suitable length of the methylene spacer. These results imply that by suitable selection of linker groups, mesogenic bolaamphiphiles possessing macroscopic chirality can be designed using a variety of naturally available sugar derivatives.