Facile fabrication and reversible color switching of thermochromic acrylic pigments based on leuco dye-BPA-dodecanol systems

Purpose This paper aims to develop a facile, microencapsulation-free thermochromic acrylic pigment (TAP) system by directly dispersing a crystal violet lactone-bisphenol A-dodecanol (CVL–BPA–OD) thermochromic pigment (TP) into commercial acrylic paints and to evaluate binder compatibility and colorimetric switching performance. Design/methodology/approach A CVL-BPA-OD TP was prepared by melt-mixing (80°C, 12 h; 1:4:100 molar ratio). TP was incorporated into acrylic paint at 5–30 Wt.% (TP:acrylic = 5:95–30:70) and coated on glass. Thermochromic behavior was assessed by image-based Commission Internationale de l’Éclairage (CIE) L*a*b* color analysis (ΔE*) from 5–60 °C. Interactions and morphology were examined by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM), while solid-state fluorescence tracked thermally induced switching. Findings TP showed reversible color switching from dark blue (∼50°C) to light blue (∼60°C) and colorless (∼70°C), with full recovery on cooling. TAP coatings exhibited reversible color variation from 5–60°C, and the optimal TP:acrylic ratio of 30:70 (w/w) delivered the highest optical contrast (Δ E* ≈ 42 at 55°C) with a distinct green → yellow transition and recovery. ATR-FTIR/SEM indicated physical compatibility without chemical reaction, and fluorescence supported reversible CVL ring-closure/opening. Research limitations/implications Future work should quantify long-term durability under accelerated aging (UV, humidity), abrasion and extended thermal cycling on diverse substrates. Practical implications The TAP system enables scalable decorative and temperature-indicator coatings using readily available acrylic paints. Social implications Accessible thermochromic coatings may support safer, more intuitive visual temperature indicators for consumer and packaging uses. Originality/value This work demonstrates a low-cost, processing-simple route to microencapsulation-free TAPs, explicitly linking pigment-binder compatibility to reproducible colorimetric switching for practical smart-coating applications.