Self-Emulsion Polymerization of 4-Vinylpyridine-Incorporated Polymer Particles for Structural Color Materials

Abstract

4-Vinylpyridine (4VP)-incorporated polymer particles are prepared via self-emulsion polymerization (SEP) and the optical property of the particles is analyzed. Mechanism of SEP in the comonomer system is investigated with 4VP and comonomers such as styrene (St) and methyl methacrylate (MMA). It is verified that the polarity of 4VP in slightly acidic water increases that it rapidly grows to amphiphilic oligomer chains and forms particle nuclei. The rapid nucleation boosts the consumption of hydrophobic comonomers; thus, highly monodisperse particles are formed. The high polarity of 4VP at the initial stage of the polymerization results in the 4VP-rich particle core which allows the insertion of optical materials inside the spherical particles without damaging the surface property. The functionality of the pyridine groups in the particles is used to improve, modify, or apply the scattering property of the colloids for the functional structural color materials. Cation adsorption property of the pyridine groups is applied to make heavy metal ion-responsible colorimetric sensors that reveal colors by controlled Mie scattering of gaseous phase colloid. Also, it is used to grow noble metal nanoparticles inside the polymer particles to remove incoherent scattering from the reflection of the glass phase colloids by the surface plasmon resonance and to selectively exhibit the colors of the coherent scattering. In situ formation of hydrophobic metal compounds-embedded polymer particles is also investigated with the 4VP-contained SEP system. The rapid nucleation of 4VP-contained SEP distinct the nucleation step and growth step of the reaction. The transfer of the metal compounds after the nucleation step allows the stable growth of the particles because the nuclei are stabilized after the step. Superhydrophobic irradiative complexes and water-insoluble PbBr2, a precursor of organic-inorganic hybrid perovskites, are successfully embedded to the particles via SEP by adjusting the transfer time of the metal compounds to post-nucleation. The periodically arranged light emitter-embedded polymer particles show improved quantum yields, color purity, and environmental stability because of the photonic bandgap induced resonance and passivation effect of the polymer chains.