Symmetry-Breaking Nature of Self-Assembled Noncubic Double Gyroid Films and Optical Reflection
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초록
내용
In this study, we suggest that gyroid lattices in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films get distorted in non-affine and unique fashion by fast deswelling upon the solvent vapor annealing process. The fast deswelling of the swollen PS-b-PMMA gyroid film brings about z-directional contraction of the three-dimensional lattices, where the lateral dimensions remain unchanged. The 2D grazing-incidence X-ray scattering (GISAXS) patterns of our noncubic gyroid films and precise peak indexing reveal several forbidden diffraction spots that would not be found for a cubic gyroid structure. From the GISAXS results, we extract electron-density difference maps and reconfigured level-set coefficients to elucidate the lattice distortion. Furthermore, the forbidden reflections appear in the UV-vis absorbance spectra as reflectance peaks, in which refractive index variations through material substitutions modulate the reflectance peaks.