Effect of stabilizers on the stability enhancement of naturally occurring dye incorporated in clay interlayer

Abstract

Naturally occurring dyes are expected as an environmentally- and eco-friendly colorant. The limitation of the usage by their low stability can partially be solved by the incorporation into inorganic host materials. However, the stability of the dye-inorganic host composites has still been insufficient. In this study, further stability enhancement of the dye composite is tried by adding several phenolic compounds as a radical scavenging stabilizer. The photostability and thermal stability of β-carotene incorporated in the organoclay interlayer is successfully improved especially when the stabilizer molecules can be efficiently intercalated together with the β-carotene. For rather slow rate of degradation, the phenolic compounds having hindered structure showed higher stabilization effect, whereas for the fast degradation, non-hindered phenols showed high efficiency. The difference in the effectiveness as a stabilizer can be explained both by the stability of the intermediate phenoxy radical species and by the steric hindrance. As a stabilizer of environmentally friendly dye composite materials, naturally occurring gallic acid and vanillic acid are the most preferrable compounds for the present composites.