Relationship between Solvent Composition Shifts of Plant-Derived Photochromic Solutions and their Photochromic Performance

Abstract

A solution composed of 3-deoxyanthocyanidin extracted from sorghum shell, a weakly acidic buffer solution, and dipropylene glycol showed photochromism. For the industrial use of this natural photochromic dye, solidification or pigmentation is necessary. However, there is a concern that the photochromic performance may deteriorate due to the change in solution composition through the process. In this study, we investigated the effect of composition shifts of the dye solution, namely solvent volatilization, water loading, and acid, base or polyvalent cation contamination on the photochromic performance.

Even when most of the water evaporated from the dye solution, neither the pH nor the photochromic properties of the solution changed. In contrast, when a large amount of water, acid, or base was mixed into the solution, the pH of the solution shifted, and deterioration in the photochromic performance was observed. Additionally, a small amount of polyvalent cations contaminating the dye solution shifted the solution to a more acidic solution, and the photochromic performance decreased. In this case, it was possible to recover the photochromic performance by altering the buffer solution used for the solution preparation to a slightly more basic solution.