X-RAY AND OPTICAL INVESTIGATIONS OF THE DISLOCATION DOMAINS IN FERROELECTRIC LIQUID-CRYSTALS

In ferroelectric liquid crystals with high enough spontaneous polariza tion P-s greater than or equal to 50 nC . cm(-2) the formation of spec ial periodic structure takes place after switching off the moderate va lue of the electric field. There are dislocation walls which separate the regions of inclined smectic layers with the opposite signs of incl ination angle delta for neighbour regions (domains). We have found tha t 1) angle delta is proportional to the value of the spontaneous polar ization, 2) the period D of the dislocaton walls is inversely proporti onal to P-s(2), 3) during the electric field treatment the periodicity of domains and the tilt-angle delta of the inclination of smectic lay ers can differ essentially in the hulk of FLC layer and near the elect rode surfaces. Complicated character of SSFLC switching can he related with the interference of bulk and surface dislocation walls. The role of the charged dislocation walls in the phenomenon of volume bistabil ity is also discussed.