Tuning the Properties of Photonic Films from Polymer Beads by Chemistry

Abstract

This paper describes the preparation of monodisperse colloids from various methacrylates. These colloids sediment well on glass slides and formsin the dried stateslarge threedimensional face-centered cubic photonic crystal films with Bragg reflection in the visible region. Depending on crystallization conditions, the domain sizes vary between 50 and 300 µm. By cross-linking the polymer within the colloids, it is possible to increase the thermal stability of the polymeric photonic structure tremendously (up to 1 h at 200 °C). These photonic structures soften above T g (rubbery photonic structure), but they cannot fuse. Crosslinked colloids from poly(tert-butyl methacrylate) can either thermally or chemically be modified. During thermal treatment (above 200 °C) the colloids shrink, as isobutene is split off. This allows a change of the lattice constant and the reflection color of an already crystallized dry photonic film. The acid-catalyzed cleavage of the ester bond allows the conversion of existing photonic structures into photonic crystals from core-shell colloids with hydrophilic polyelectrolytes in the shell.

Optimization of Emulsion Polymerization for Submicron-Sized Polymer Colloids towards Tunable Synthetic Opals

“…Number of pioneering literatures have reported that the polymeric microspheres having the diameters in the range of 100 ~ 400 nm fall in such "photonic grade" microspheres. 14,16,[24][25]27 We have confirmed that the polymer microspheres from the acrylic monomer such as MMA, tBMA within the size of photonic grade could be conveniently synthesized without the use of surfactant which usually takes part in the emulsion polymerization. 24 In SFEP, the initiation takes place by scission of potassium persulfate, followed by radical attacks to some monomers to form charged oligomers.…”

“…14,16,[24][25]27 We have confirmed that the polymer microspheres from the acrylic monomer such as MMA, tBMA within the size of photonic grade could be conveniently synthesized without the use of surfactant which usually takes part in the emulsion polymerization. 24 In SFEP, the initiation takes place by scission of potassium persulfate, followed by radical attacks to some monomers to form charged oligomers. Such oligomers behave as surfactants to stabilize monomer droplet (micelle), resulting in the growth of polymer microsphere in a similar manner as "classical" emulsion polymerization.…”

“…The monodisperse polymeric microspheres of photonic crystal grade can be obtained by emulsion polymerization technique. 24 Emulsion polymerization is relatively simple and versatile since various monomers are applicable which can be radically polymerized through addition mechanism. There have been a lot of studies on emulsion polymerization from various points of view such as size control, functionality control, cost, and so on.…”

“…There have been a lot of studies on emulsion polymerization from various points of view such as size control, functionality control, cost, and so on. [24][25][26] Recently, Egen et al have reported a simple emulsion polymerization method without using an amphiphilic surfactant otherwise necessary for controlling the size of microspheres. 24 However, comprehensive investigations including the synthesis, the colloidal crystallization, and the optical characterizations are hardly found.…”

“…Poly(methyl methacrylate) (PMMA) and poly(t-butyl methacrylate) (PtBMA) colloidal particles were synthesized by surfactant-free emulsion polymerization (SFEP) by modifying the method reported by Egen et al 24 Thermally dissociable initiator, PPS was dissolved in DI water and transferred to a 50 mL two-neck round bottomed flask, the temperature of which has been maintained at 90 o C in silicone oil bath. The aqueous initiator solution was purged with nitrogen (N2, 99.99%, Donga Gas Inc.) for 30 min with stirring.…”