부산대학교 도서관

In order to investigate the influence of two or more polar groups on packing modes of molecules, crystal structures have been determined for isomeric mesogens with different directions of two ester linkages, C_8H_<17>O-C_6H_4-X-C_6H_4-Y-C_6H_4-OC_8H_<17>, where X=COO and Y=OOC for I, X=OOC and Y=COO for II and X=COO and Y=COO for III. Moreover, the crystal structure of C_8H_<17>O-C_6H_4-COO-C_6H_4-COO-C_6H_4-OCH_3 (IV) has also been determined. In crystal I, molecules are arranged so that moieties conjugated from C=O to an alkoxyl O atom via a benzene ring have an antiparallel arrangement, resulting in an imbricated structure. Crystal II and III have lamellar structure with a small tilt, in which ester linkages of adjacent molecules come close each other. In crystal IV, OCH_3 and an ester linkage are close between adjacent molecules, leading to an imbricated structure. The feature of the crystal structures are closely related to the phase sequences.