Buckling instability of smectic lamellar phase affected by the constituent molecular shape

Abstract

Buckling instabilities and their collapse are major issues for the lamellar materials, and its mechanism at the molecular scale has not been fully addressed. We study the evolution of the lamellar structure under the lateral compression through the coarse-grained molecular dynamics approach. We investigate the influence of the molecular shape on their collapse based on explicit representation, and find that the critical strain of their collapse depends on the molecular shape. When the molecular length is smaller than the tip width of the chevron-like collective structure, the directors can be aligned in two possible directions parallel and perpendicular to the layers. This variation of molecular orientation causes the generation of isotropic domain wall. On the other hand, when the length of the molecules is longer than the tip width, the parallel misalignment is suppressed and the lamellar structure is more stable. Therefore, the ratio of the molecular length to the tip width affects the buckling instability of the lamellar structures.