Flexo and Ferro-Electricityobservation of Ferroelectrical Monodomains in the Chiral Smectic C Liquid Crystals

We have determined, on monodomain samples oriented by an electric field, the tilt angle of molecules inside the layers of ferroelectric smectic C phase of some chiral compounds (DOBAMBC, OOBABCC, HOBACPC, DOBAMBCC, TDOBAMBCC) and we have studied the temperature dependance of this angle. The sign of the permanent electric dipole of the molecules has also been determined. We have specified the pitch of the helix obtained without electric field.