Spirooxazine Photochromic Dye – Ranbar Brown DP7030

Ranbar Brown DP7030 is a colorless-to-brown photochromic dye based on spirooxazine. Upon exposure to ultraviolet light, typically from the sun or a UV lamp, it undergoes a chemical change, transitioning from transparent to brown. When the UV light source is removed, the dye reverts to its transparent state.

Depending on the application, photochromic dyes can undergo repeated color changes, with the number of cycles primarily determined by the substrate embedded with the photochromic dye. They can also transition from one color to another by combining with permanent pigments.

The spiro form of oxazine is a colorless dye, the conjugated system of oxazine and another aromatic part of the molecule are separated by a sp3 hybridized “spiro” carbon atom, upon UV irradiation, the bond between the spiro carbon and the oxazine is broken, the ring opens up, the spiro carbon achieves an sp2 hybridization and becomes planar, followed by a rotation of the aromatic group, whose π-orbitals are aligned with the rest of the molecule. Finally, a conjugated system is formed with the ability to absorb visible light photons, resulting in colorful colors. When the UV source is removed, the molecule gradually relaxes to the ground state, the carbon-oxygen bond is re-formed, the spiro carbon becomes sp3 hybridized again, and the molecule returns to its colorless state.

The form of this photochromic dye is thermodynamically unstable, and unless cooled to low temperatures, it will revert to its stable form in the dark. Like most organic dyes, their lifespan is also influenced by exposure to ultraviolet radiation, and they are susceptible to degradation by oxygen and free radicals. Incorporating the dye into a polymer matrix, adding stabilizers, or providing barriers to oxygen and chemicals can extend the lifespan of the photochromic dye.