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Controlled structural color visibility was achieved using colloidal particles covered with a catechol polymer shell layer. When exposed to ammonia vapor, the pellet sample obtained by assembling the particles extended the conjugated length of the shell polymer, giving the particles the ability to absorb scattered light in situ and improving the visibility of structural colors.

Monodisperse polystyrene particles were prepared by enzymatic emulsifier-free emulsion polymerization using a horseradish peroxidase (HRP)/H₂O₂/β-diketone system in water. The resultant polymer particles were stabilized by the β-diketone moieties located at the surface of the particle. Enzymatic emulsifier-free emulsion polymerization might offer a practical method for the preparation of polymer particles under mild enzymatic conditions (that is, room temperature and surfactant-free).

Polyethylene glycol-containing hematin (PEGylated hematin) was prepared using the Mitsunobu reaction as a water-soluble biomimetic catalyst for polymerization of arbutin in a phosphate buffer solution of pH 7.0. The structure of polyarbutin obtained was characterized by ¹H nuclear magnetic resonance and infrared spectroscopy. PEGylated hematin showed high catalytic activity for arbutin polymerization, indicating that it is a better catalyst compared with horseradish peroxidase.

Melanin, a black component of human hair, plays an important role in bright structural colorations in nature. Polydopamine-based artificial melanin particles, inspired by natural melanin and its important role in structural coloration, were used to produce bright structural colors by controlling light reflection and absorption. A variety of structural coloration characteristics have become possible through our investigations of the assembly structure, composition, shape, and application of artificial melanin particles.

This focus review describes a novel research concerning horseradish peroxidase (HRP)-mediated enzymatic polymerization under aqueous heterogeneous conditions as follows: (i) monodisperse polymer particles were prepared by enzymatic miniemulsion polymerization using surfmer (surfactant+monomer). (ii) Polymer particles stabilized by β-diketone moieties were prepared by enzymatic emulsifier-free emulsion polymerization. (iii) A novel method of surface-initiated enzymatic graft polymerization was used to synthesize core-shell particles.

Doping lanthanides into lamellar crystals of diacetylene derivatives with terminal carboxylic acids reorganized the lamellar structure and dramatically changed the crystal morphology. Detailed investigation of the crystal growth process revealed that the complexes of lanthanide and diacetylene derivatives, which are slightly formed in the solution phase during lanthanide doping, may act as a pseudonuclear agent and change the morphology of the lamellar crystals. Furthermore, the morphology changes of the lamellar crystal films significantly altered surface properties such as film appearance and water repellency.