  A series of asymmetric dimers with an odd number of atoms in the spacer were
found to form different types of twisted structures despite being achiral. The
formation of a variety of helical structures is accompanied by a gradual
freezing of molecular rotation. The tight pitch heliconical nematic (NTB) phase
and heliconical tilted smectic C (SmCTB) phase are formed. In the lowest
temperature smectic phase, HexI, the twist is expressed through the formation
of hierarchical structure: nano-scale helices and mesoscopic helical filaments.
The short pitch helical structure in smectic phases is confirmed by resonant
x-ray measurements.
