Stripe instabilities in menisci of free-standing smectic films with a direct transition from smectic C to an isotropic or nematic phase

ABSTRACT

Regular periodic stripe patterns that are found in the menisci of smectic C and C freely suspended films were described first by Meyer and Pershan (Solid State Commun. 13 (1973)) more than 40 years ago, but their physical origin is still under debate. Loudet et al. (Phys. Rev. Lett. 106 117, 802 (2011)) proposed a layer dilatation model to explain their formation. Our observation of such patterns in films with a direct transition from smectic C to a nematic or isotropic phase is in sharp conflict with that model. Moreover, we demonstrate the disappearance of the patterns at the transition from synclinic to anticlinic smectic C phases. An essentially different explanation of the physical mechanism of the stripe formation must be sought. We propose potential sources of the instability.

Graphical Abstract

KEYWORDS:

• Smectic free-standing films
• spontaneous pattern formation
• dislocations
• polarising microscopy

Acknowledgements

We thank J.-C. Loudet for interesting discussions of our results and useful hints.

Notes

1. Some confusion arises because the authors of Ref. [1] explicitly mention a nematic–SmC transition in their paper. However, this statement seems to contradict the mesomorphism given in Ref. [12], particularly Fig. 7 of that paper. The second reference in Ref. [1] announcing details of the material seems to be non-existent.

Additional information

Funding

Financial support by Deutsche Forschungsgemeinschaft within projects STA 425/28-2 and ER 467/8-1 and by Deutsches Zentrum für Luft- und Raumfahrt within project 50WM1430 is kindly acknowledged..