Azacyclic‐Modified Polyurethane Acrylate Films With Heat Resistance for Flexible Display Encapsulation

ABSTRACT Polyurethane acrylate (PUA) films are widely utilized in flexible electronics and optical devices owing to their mechanical robustness, elasticity, and high transparency. However, their performance rapidly deteriorates under thermal stress, severely limiting their long‐term reliability. Here, we report the synthesis of a novel azacyclic polymer, 3,3′,3″‐((1,3,5‐triazine‐2,4,6‐triyl)tris(azanediyl))triphenol (TTT), which is incorporated into PUA matrices to enhance heat resistance. The resulting azacyclic‐modified PUA film exhibits markedly improved thermal stability, increasing the onset degradation temperature by approximately 20°C. Furthermore, the tensile strength of the modified film demonstrates a 61% enhancement compared with the unmodified counterpart after exposure to 60°C for 4 h. Notably, the modified PUA maintains over 90% optical transmittance without haze after being aged at temperatures ranging from 50°C to 120°C for 4 h, thereby preserving the visual clarity required for display applications. This study provides a novel strategy for fabricating heat‐resistant PUA films, offering a promising pathway toward next‐generation encapsulation materials for flexible and wearable electronic systems.