Do lamellar liquid crystals flow like solids?

The role of dislocations in the deformation or flow of lamellar-phase liquid crystals is critically examined in the light of two studies. In the first, dislocation climb is directly observed under a compression normal to the layers. Two regimes of climb are evidenced. In the second study, lamellar phases are sheared in a rotating rheometer. Gliding screw dislocations carry a vorticity tensor component, which counterbalances plastically the applied vorticity. The similarities and differences between dislocation processes in solid and lamellar liquid crystals are discussed.