Solvatochromic Coatings with Self-Cleaning Property from Palygorskite@Polysiloxane/Crystal Violet Lactone

Organic allochroic materials have wide potential applications in various fields but have so far been limited because of their low stability and low and slow switching reversibility. Because of the extraordinarily high durability of Maya Blue and the superhydrophobic lotus leaves, the new solvatochromic and self-cleaning coatings with intense blue color are fabricated by the combination of polysiloxane-modified palygorskite (PAL@POS) and crystal violet lactone (CVL) via solid-state grinding. The coatings are characterized using scanning electron microscopy, diffusive reflection UV-vis spectra, and other analytical techniques. The hydrogen bonding of the hydroxyl groups of PAL@POS with the carboxylate groups of CVL⁺ is the origin of the intense blue color. The interruption of the hydrogen bonding by the vapor of solvents results in rapid discoloration of the coating. On the other hand, the evaporation of the solvents from the coating results in complete recovery of the original color by restoring the hydrogen bonding between PAL@POS and CVL⁺. The polarity, hydrogen bonding ability, and volatility of the solvents determine the solvatochromic properties of the coating. The PAL@POS/CVL coatings feature high reversibility and rapid switching between the colored and colorless states induced by the vapor of various solvents. Also, the coatings are superhydrophobic with fine self-cleaning properties and high durability in different environments. Moreover, the CVL content in the coating is controllable and can be as high as 4.8 wt %.