Hedlund Keith G, Martinez Vikina, Chen Xi, Park Cheol S, Maclennan Joseph E, Glaser Matthew A, Clark Noel A
Department of Physics, University of Colorado, Boulder, Colorado, 80309, USA.
Phys Chem Chem Phys. 2024 Dec 18;27(1):119-128. doi: 10.1039/d4cp03425b.
We show that stable, freely suspended liquid crystal films can be made from the ferroelectric nematic (N) phase and from the recently discovered polar, lamellar SmZ and SmA phases. The N films display two-dimensional, smectic-like parabolic focal conic textures comprising director/polarization bend that are a manifestation of the electrostatic suppression of director splay in the film plane. In the SmZ and SmA phases, the smectic layers orient preferentially normal to the film surfaces, a condition never found in typical thermotropic or lyotropic lamellar LC phases, with the SmZ films exhibiting focal-conic fan textures mimicking the appearance of typical smectics in glass cells when the layers are oriented normal to the plates, and the SmA films showing a texture of plaquettes of uniform in-plane orientation where both bend and splay are suppressed, separated by grain boundaries. The SmA phase can also be drawn into thin filaments, in which X-ray scattering reveals that the smectic layer planes are normal to the filament axis. Remarkably, the filaments are mechanically stable even if they break, forming free-standing, fluid filaments supported only at one end. The unique architectures of these films and filaments are stabilized by the electrostatic self-interaction of the liquid crystal polarization field, which enables the formation of confined, fluid structures that are fundamentally different from those of their counterparts made using previously known liquid crystal phases.
我们表明，可以从铁电向列相（N相）以及最近发现的极性层状SmZ相和SmA相制备稳定的、自由悬浮的液晶膜。N相膜呈现二维近晶状抛物线焦锥织构，包含指向矢/极化弯曲，这是膜平面内指向矢展曲的静电抑制的表现。在SmZ相和SmA相中，近晶层优先垂直于膜表面取向，这在典型的热致或溶致层状液晶相中从未发现，SmZ相膜呈现焦锥扇形织构，当层垂直于板取向时，模仿玻璃盒中典型近晶相的外观，而SmA相膜显示出均匀面内取向的斑块织构，其中弯曲和展曲均被抑制，由晶界分隔。SmA相还可以被拉成细丝，其中X射线散射表明近晶层平面垂直于细丝轴。值得注意的是，即使细丝断裂，它们在机械上也是稳定的，形成仅一端支撑的独立流体细丝。这些膜和细丝的独特结构通过液晶极化场的静电自相互作用得以稳定，这使得能够形成与使用先前已知液晶相制成的对应物根本不同的受限流体结构。
