Effect of photopolymerization and color phase transition on the structural color expression of long-chain diynoate-modified titanium dioxide multiparticle layers

A film-type colorant that exhibits color through both absorption and scattering of visible light has been created using multilayers of organo-modified inorganic nanoparticles. Using titanium dioxide (TiO 2 ) nanoparticles surface-modified with a long-chain diynoic acid derivative, a single-particle layer was prepared and layered to exhibit structural color, followed by photopolymerization by ultraviolet (UV) irradiation. Before UV irradiation, the diacetylene-modified TiO 2 prepared in a stepwise manner exhibited a clear gradation of structural color. These stepped multilayers exhibited a blue absorption band in the UV-Visible (UV–vis) absorption spectrum when irradiated with UV light at 254 nm. Therefore, color-developing nanoparticle layers that scattered and absorbed visible light were obtained. The photopolymerized stepped multilayers gradually transformed into films that showed a red absorption band when annealed at 50 °C. The red absorption band reaches its maximum value after 24 h of annealing and gradually attenuates thereafter. However, the gradual color change owing to the difference in the number of layers was not lost, suggesting that the color derived from the structural color did not fade. As a result, it has obtained organized films of layered nanoparticles that exhibited color through the absorption and interference of visible light and was structurally stabilized through the formation of bonds between the modified chains. • Colorant produced by both absorption and interference of visible light was created. • Structural color occurred by a multilayer film of organo-modified TiO2. • The hue was changed by photopolymerization of the diynoic acid as modified chains. • The structural stability was improved by photopolymerization. • Regularity of the multilayers retained during color phase transition.