Dielectric measurements on two samples of banana-shaped molecules showing a B2and a B7phase were carried out. The low frequency dispersion in the B2phase 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 B7phase 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 B7and in the low temperature phase Bx.