Surface structures of hybrid aligned liquid crystal network coatings containing reverse tilt domain

Abstract

Controlled shape changes of polymerized liquid crystalline coatings is often achieved via prepatterning the molecular orientation of liquid crystal (LC) monomers at the stage of preparation. In this work, using the so-called hybrid alignment of the LC, we produce surface structures of positive Gaussian curvature of coatings without complex techniques such as photoalignment. A mixture of LC monomers coated onto a glass plate with planar alignment of the director is exposed to air, which promotes vertical alignment. The competing planar and homeotropic boundary conditions result in a) thickness dependent director and b) spontaneous formation of spindle-like regions, limited by disclination loops, that are called the reverse tilt domains (RTDs). The disclination separates different director configurations inside and outside the RTD. The RTDs produce relatively big protrusions (100 − 600 nm) of the LC network coating. Actuation of the coating by heat increases the amplitude of RTD protrusions.