Opal-like structures based on polymethylmethacrylate submicrosphere

In this work, 2D and 3D metamaterials and colloidal crystals are made from submicron-sized polymethylmethacrylate particles with a polydispersity of less than 5% by self-assembly. Morphological features of the obtained samples were studied using an ultra-high-resolution FE-SEM Hitachi S-5500 scanning electron microscope. Three different surface areas of 3D opal were investigated using the spectroscopy of the reflected light with the angular resolution. The spectra were measured in the range of 400-1250 nm. The above methods revealed a highly ordered structure. A narrow particle size distribution was revealed. The average particle diameter, packing density, q-factor, and reflectivity of the samples were determined. Based on the experimental reflection spectra, the dependence of the maximum reflectivity wavelength on the angle is approximated using the modified Bragg-Snell law. Based on this dependence, the wavelength of the maximum reflection at normal incidence, the particle diameter, and the filling factor were determined. The wavelength of the center of the photonic bandgap is calculated for the highly ordered surface at normal incidence. The experimentally measured the full width of the peak at a half maximum for the best sample was 70 nm, and the q-factor was 12.4. The calculated filling factor for the highly ordered opal was 87%. The average particle diameter obtained by the approximating the reflection spectra is in excellent agreement with the values obtained by electron microscopy. The most interesting result is that the reflectivity of the surface at normal light incidence can reach 98%, and this value depends on the filling factor – the density of the package.