| dc.description.abstract | In this study, photonic crystals were fabricated by self-assembled polystyrene submicrosphere (PS sphere) with different amount of nanospheres and their opal and mechanic properties were investigated.
First, PS sphere (185.4nm) and nanospheres were prepared by soap-free emulsion polymerization at boiling condition. Styrene, n-butyl methacrylate, and butyl acrylate were used as monomers in the presence of sodium p-styrenesulfonate to prepare nanospheres. According to glass transition temperature (Tg), nanospheres were divided into hard nanospheres (H100 and H58) and soft nanospheres (S26, S06, S-17 and S-54). The particle size, polydispersity index (PDI) and refractive index of nanospheres was measured by dynamic particle size analysis (DLS) and refractive index detector (RI). The results showed that nanospheres had narrow PDI, about 30nm diameter and 1.4 to 1.6 RIs.
Surface morphology, particle size (Dn), and wavelength (λ) of photonic crystals were determined from scanning electron microscope (SEM), effective refractive index equation and modified Bragg’s law. The reflection wavelength (λmax) was measured from ultraviolet-visible spectroscopy (UV-Vis). In addition, stability of soft nanospheres in PS sphere solution was measured by DLS.
SEM results showed that hard nanospheres were distributed around PS spheres in their photonic crystals. On the other hand, soft nanopheres were coated onto PS spheres in their photonic crystals. With increasing weight fraction of hard or soft nanospheres in the photonic crystals, Dn and λ were increased. The value of λmax was corresponding to that of λ.
The mechanical property of the photonic crystals was measured by the pencil hardness test. The result showed with increasing Tg and the weight fraction of nanospheres, the pencil hardness was increased. The opal film prepared by PS sphere with 20% S-54 nanpsphere had the highest pencil hardness, H.
Finally, inverse opal templates were fabricated by adding silica precursor into photonic crystals, then calcinated. SEM results showed that hard nanospheres were distributed around PS spheres and soft nanospheres were coated onto PS spheres in their photonic crystals, respectively. | en_US |