Mecanocromismo associado à utilização de espiropirano como agente de ligação cruzada em matrizes poliméricas

Abstract

This work aimed to develop polymeric materials with mechanochromic properties for application as stress-sensing surfaces. Therefore, two spiropyran derivatives, named SPOH₂ and SPV, were synthesized, with particular emphasis on SPV, which was designed with methacrylate functional groups at its termini, enabling its use as a cross-linking agent in the polymerization of vinyl systems. Proton nuclear magnetic resonance (¹H NMR) and infrared spectroscopy (FTIR) were used to analyse the derivatives, verifying their anticipated structures. UV–Vis spectroscopy in solution revealed the absence of photochromic and solvatochromic behavior, indicating non-responsive characteristics under these conditions. The SPV derivative was subsequently employed as a cross-linker in the synthesis of polymeric materials based on polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(ethyl acrylate) (PAE). The obtained materials were characterized by FTIR and thermogravimetric analysis (TGA), confirming its structure and thermal stability. Among them, the PS-SP material was further investigated in greater detail and exhibited selective mechanochromic behavior. The color change induced by mechanical stress was observed visually and further confirmed by diffuse reflectance UV–Vis and emission spectroscopy, with no significant response under UV irradiation. These results demonstrate the successful development of a material capable of functioning as an optical sensor of structural integrity, providing an effective mechanism for self-reporting mechanical damage.