Full‐Color Electrophoretic Display Using Charged Colloidal Arrays of Core–Shell Microspheres with Enhanced Color Tunability in Non‐Polar Medium

Abstract

In this study, core–shell microspheres of poly(methylmethacrylate) (PMMA) and poly(t‐butylmethacrylate) (PtBMA) are synthesized and dispersed in a non‐polar medium exhibiting a structural color in the visible range. The charge stabilization of the PMMA–PtBMA microsphere is achieved because of preferential adsorption of the charged inverse micelles of aerosol‐OT (AOT) on the microsphere surface. While the PtBMA shell enables the dispersion of the microspheres in isoparaffinic fluid, the PMMA core provides an enhanced refractive index contrast with the medium. In comparison to PtBMA‐only microsphere, incorporation of PMMA core not only increases the average refractive index but also increases the surface charge density of the microsphere, which is attributed to strong attraction between the inverse micelles and the microsphere. The optimized crystalline colloidal array (CCA) of the PMMA–PtBMA microsphere shows stronger structural colors than those of the PtBMA‐only spheres because of an enhanced index contrast with the liquid medium, and an improved color tunability is also achieved. A CCA exhibits approximately 50% light transmittance, demonstrating a semi‐transparent display. The repeated voltage biases proved that a CCA has excellent stability. Finally, a low‐angular dependency of the PMMA–PtBMA CCA is confirmed, which is an advantageous feature as an electrophoretic display.

Stimulus‐Responsive Photonic Crystals for Advanced Security

“…In a particular electric field, the electric stacking force induced by the electric field is balanced by the electrostatic repulsion between the charged colloids, resulting in a certain interparticle distance. [126] The change in the dynamic balance between the electric stacking force and electrostatic repulsion force is the main reason for the tunable structural color. For instance, Sun et al constructed core-shell SiO 2 @TiO 2 colloidal nanoparticles with electrochromic properties.…”

In Situ Dynamic Study of Color-Changing in Liquid Colloidal Crystals for Electrophoretic Displays

“…Song et al used oxygen plasma treatment to obtain electrodes with uniform charge distribution, which were found to be beneficial to the display brightness improvement. On the other hand, the water can be replaced with organic solvents that are more stable to an electric field. , Propylene carbonate, ethylene glycol, or nonpolar isoparaffinic fluid supported by sodium di­(2-ethylhexyl) sulfosuccinate have been tried in preparation of the ECPC devices with good compatibility. , …”

“…21,23 Propylene carbonate, 30 ethylene glycol, 31 or nonpolar isoparaffinic fluid supported by sodium di(2-ethylhexyl) sulfosuccinate have been tried in preparation of the ECPC devices with good compatibility. 39,40 However, it is still challenging to fabricate ECPC devices with simple composition, dynamic color, and excellent performance for multifunctional use. Meanwhile, the electrically responsive kinetic and corresponding mechanism of the electrophoretic ECPCs may provide guiding significance for the development and expanded application of the dynamic ECPC devices, but it is still hard to be studied in real time.…”

Span 85-Based Macromolecular Stabilizer for the Preparation of PMMA Colloidal Particles in a Nonpolar Media

“…For example, the electrolysis of water occurs at rather low over potential (∼1.5 V). The dissolution and deposition of metal impurities lead to the contamination of the electrodes. , On the other hand, some polymer particles such as poly­(methyl methacrylate) (PMMA) in nonpolar media are useful model systems to study fundamental condensed matter physics problems, such as nucleation, crystallization and melting, glass transition, colloidal gels, and so on. − Marked with fluorescent dyes, these particles can be directly observed by confocal microscopy in the real space, and thus, their structure and dynamics can be studied in dilute or even concentrated systems. − In these applications, stable dispersion of colloidal particles against aggregation is of paramount importance, and high monodispersity is expected.…”

“…Polydimethylsiloxane (PDMS)-based macromolecules or block copolymers have been used for the dispersion polymerization of PMMA, , and the biggest benefit is that PDMS polymers with various molecular weights and reactive end groups are commercially available. Other stabilizers mainly include some graft or block copolymers based on polyethylene, polypropylene, or polyisobutylene. − Despite these advances, especially motivated by the requirement of the particle-based electrophoretic display technique, ,,− new stabilizers that can be easily synthesized and that can provide sufficient functionalities are highly desired.…”