Enhanced Mechanical Stability of Water-Based Peel-Off Nail Polish Through Riboflavin Phosphate-Mediated Visible Light Photocrosslinking

Water-based peel-off nail polishes offer environmental and safety advantages but often suffer from poor mechanical properties. This study investigated the effect of visible-light-induced photocrosslinking with riboflavin phosphate (RFP) on the mechanical properties and adhesion of water-based peel-off nail polish films. Polyurethane films that contained various concentrations of RFP (0-0.1%) were prepared by combining two commercial water-based polyurethane dispersions and characterized through tensile testing, rheological analysis, and adhesion measurements. Under large deformation, the photocrosslinked films showed significantly enhanced mechanical properties, with the highest RFP concentration (0.1%) exhibiting a 54% increase in tensile strength and a 94% increase in Young's modulus compared with the control, which reflected a transition from physical to covalent network dominance. Rheological analysis under small deformation revealed the formation of complex network structures, where lower RFP concentrations maintained a higher chain mobility beneficial for adhesion, while higher concentrations created more stable networks with enhanced thermal stability, which maintained 50% of the initial storage modulus up to 100 °C. The films exhibited biocompatibility across all RFP concentrations in the cell viability tests, and the straightforward preparation process that used commercially available materials suggests immediate potential for industrial implementation. These results demonstrate that RFP-mediated visible light photocrosslinking offers a promising approach for developing high-performance, environmentally friendly nail polish formulations that combine enhanced durability with user safety and manufacturing practicality.