Bend elastic constant in ferroelectric free standing films of tilted smectics

A texture of circular concentric disclination walls is produced in a smecti c C* free standing film on applying an in-plane ac electric field. Intensit y light profiles taken in the radial section of the circular walls allows u s to evidence modulations of the tilt of the molecules. These molecular til t angle modulations are due to a new elastic term K*c(2)(rote).N in the fre e energy. We deduce the linear bend constant K*, which originate from the c hiral property of the system. We find K*/b similar to 2.5 mum.