Collective Dynamics in Some Phases Consisting of Banana-Shaped Molecules

Abstract

Dielectric measurements on two samples of banana-shaped molecules showing a B₂ and a B₇ phase were carried out. The low frequency dispersion in the B₂ phase is interpreted as a collective motion of ferroelectric clusters and the high frequency one as the reorientation of single molecules with a strong positive dipole correlation. In the B₇ phase a, soft mode-like“ behavior was detected pointing to an additional phase transition. AFM measurements support the existence of helical super-structures which probably appear in B₇ and in the low temperature phase B_x.

Key Words:

• Dielectric measurements
• banana-shaped molecules
• super-structures