Highly ordered defect arrays of 8CB (4′-n-octyl-4-cyano-biphenyl) liquid crystal via template-assisted self-assembly

Abstract

A synthetic rod-like smectic liquid crystal containing a rigid aromatic group and semi-fluorinated chains generates well-ordered toroidal structures called toric focal conic domains (TFCDs) as self-assembling building blocks when confined within rectangular micro-channels. However, in the case of common smectic liquid crystals with alkyl-terminated chains, the ordered arrangement of TFCDs is challenging work because of their high mobility and low elasticity. Here, we present a simple method to fabricate highly mono-dispersed periodic patterns using the most commonly used smectic liquid crystal, 8CB (4′-n-octyl-4-cyano-biphenyl), by changing the geometry of confined microchannel with a controlled surface polarity. This is attributed to the combining effects between antagonistic surface anchoring conditions and precisely directed molecular orientation onto inclined side walls of a trapezoidal channel. Furthermore, size and ordering of arrays of 8CB can be simply controlled by varying the feature dimension of bottom width (l) and depth (h) in the trapezoid-shaped channel. The use of 8CB will generalize fabrication of the spatial arrangement of TFCD arrays for future nanotechnology and liquid crystal research.