Reflection characteristics of cholesteric liquid crystal microcapsules with different geometries

The reflection properties of cholesteric liquid crystals (CLCs) encapsulated in poly(methyl methacrylate) (PMMA) by solvent evaporation were investigated both experimentally and theoretically. The geometry of the CLC/PMMA microcapsules significantly influenced their reflection characteristics. Spherical CLC/PMMA microcapsules exhibit a color corresponding to the CLC intrinsic wavelength λ0 at the center of the microcapsule with the color changing to colorless at the fringes, whereas flattened spherical CLC/PMMA microcapsules only show vivid color at their centers. By recognizing the effect of the interactions between PMMA and CLC, an alignment model was developed and analyzed. The high correlation between the experimental and modeled color data confirms a high degree of ordering of the CLC molecules inside the microcapsules. The calculated results for a single CLC/PMMA microcapsule were in good agreement with the experimental reflection spectra of the CLC/PMMA microcapsule films. These results show how the shapes of CLC/polymer composites determine their optical properties.

► Both spherical and flattened spherical CLC/PMMA microcapsules were obtained.
► The geometry of the CLC/PMMA microcapsules significantly influenced their reflection characteristics.
► An alignment model was developed and analyzed by recognizing the effect of the interactions between PMMA and CLC.
► The theoretical and experimental results of the color analysis are in good agreement.