Linear symmetric liquid crystal trimers exhibiting supramolecular chiral architectures

We prepared a homologous series of achiral liquid crystal trimers (I-n) in which two phenylpyrimidine units and one biphenyl unit were connected via flexible spacers, and investigated the physical properties. All the trimers possessing odd-numbered methylene spacers exhibited soft crystalline chiral conglomerate phases. X-ray diffraction measurements reveal that they have an intercalated layer structure. On the other hand, the trimers possessing even-numbered spacers showed nematic and smectic C phases. We investigated the surface structures of odd-membered trimers in the soft crystalline phases using scanning electron microscopy. Trimers I-3 and I-5 were found to form cylindrical tubes, whereas trimers I-7, I-9 and I-11 toroidal pits. We discuss the formation of diverse supramolecular architectures in terms of the anisotropy of the chirality transfer.