Smectic C to smectic A transition induced mechanically by the rupture of freely suspended liquid crystal films

The tilt angle of smectic C phases can be controlled by external forces of very different nature. In particular near a smectic A-smectic C transition, it is susceptible to temperature changes. It can be influenced with electric fields (electroclinic effect), and even mechanically by intra-layer stresses in elastomers. We show that capillary forces that act during the rupture of a free-standing smectic C film can trigger a smectic C to smectic A transition, which rapidly reduces the surface area of the films, concurrently increasing the film thickness. The effect occurs on the sub-millisecond scale, practically independent of film thickness and temperature. We propose that this mechanical effect could even trigger a ferroelectric to paraelectric transition in chiral phases.