Preparation, Assembly And Properties Of Polymethyl Methacrylate Microspheres

Three different functional colloidal photonic crystals (PCs) were fabricated in this dissertation which included bright structural color, heat resistance and flexibility. Bright structural color could be achieved through doping black colorants, heat resistance was accomplished by auxiliary cross-linking, and flexibility was realized by cross-link curing.Emulsifier-free polymerization was used to synthesize different size polymethyl-methacrylate (PMMA) colloidal particles varying from190nm to263nm, PC films were fabricated by heat convective self-assembly from these particles. PC films from263,235,225and190nm colloidal beads displayed red, yellow, green and blue structural color, respectively. Corresponding reflectance of these PC films reached35.6%,34.0%,41.5%and34.1%. DLS was used to measure the hydrodynamic sizes and zeta potential of the particles. Polydispersity indexes (PDI) of the obtained microspheres were less than0.1, and the corresponding zeta potential ranges from-30.1mV to-33.1mV. PDI and zeta potential results indicated that stable monodispersed emulsions were prepared. Scanning electron micrographs (SEM) were taken to observe the surface microstructures of the photonic crystal films, and the results showed that well-shaped PMMA spheres were arranged in an orderly array. By doping optimal amount acid black210, which was0.49wt%, bright structural color could be achieved. SEM, reflectance spectra indicated that doping dye could hardly affect periodicity and PBG of these colloidal PC films.Heat resistance of PMMA PC films was controlled and remarkably improved by introducing methacrylic acid as auxiliary cross-linker. Monodisperse particles that have MAA contents that varies between0wt%and25.6wt were synthesized through auxiliary cross-linking, and then were assembled to colloidal PC films by vertical-lifting. The obtained films showed green, yellow, red and light red with MAA contents increasing from0wt%to25.6wt%, and the corresponding reflectance were45.1%,29.6%,22.7%and34.1%. PMMA photonic crystal films with18.7wt%MAA could resist high temperature up to160℃. By doping optimal amount carbon black, which was1.63wt%, bright structural color could be achieved.Flexible colloidal PC films were realized by cross-link curing. Polydimethylsiloxane (PDMS) were infiltrated into interstice between PMMA beads and cured by heating. Comparing microstructure periodicity and optical properties of the colloidal PC films before and after cross-linking curing, the reason of red shifting and reflectance decline were analyzed. Also, we doped acid black210into the emulsion before self-assembly, and in hence the bright and flexible colloidal PC films were achieved.