Observations of Sm C Layer Undulations and Sm C Edge-Dislocations in NOBA Films

Sm C layer undulation instabilities produced by first and second-order effects have been obtained after the rapid cooling of thin (10-26 microns) homeotropic and twisted nematic NOBA films. The Sm C dilation modulus B has been approximately calculated to be around 0.32 × 10 +4 erg/cm 3 and the larger value of the Sm C elastic coefficient A 21 relative to that of A 12 has been demonstrated. A number of novel, directly-observable Sm C edge-dislocation lines (or walls) have been obtained after the rapid cooling of electrically-deformed twisted nematic NOBA films. A physical model explaining their creation has been given. The possible relaxation of the dislocation walls into Néel walls with a partial twist and further into alternating nuclei with strength ± 1 has not been observed, possibly due to the larger value of A 21 relative to that of A 12 . Possibilities for storage applications have briefly been discussed.