Descrizione principale (Inglese)

The physicochemical behavior of a polymer is fundamentally dictated by its backbone architecture and the nature of its pendant groups, making post-polymerization functionalization a critical strategy for synthesizing systems with optimized characteristics. While polyacrylonitrile (PAN) possesses excellent mechanical and thermal resilience, its hydrophobic nitrile (-CN) groups and high crystallinity often impede dye penetration, resulting in poor color retention. To overcome these limitations, researchers integrate additional monomers, graft functional groups such as polyethylenimine (PEI), or utilize a two-stage hydrolytic activation . In the latter approach, the electrophilic carbon center of the nitrile group is subjected to a progressive nucleophilic transition within a controlled alkaline environment. Spectroscopic analysis confirms that these groups hydrate into intermediate amides (-CONH2) before converting into negatively charged carboxylate (-COO-) sites. This multi-step hydrolysis significantly increases the polymer’s hydrophilicity and negative surface charge, turning a hydrophobic material into an anionic substrate suitable for heavy metal adsorption or enhanced dyeability. These carboxylate sites serve as high-affinity docking points for cationic dyes, facilitating strong ionic bonding rather than simple physical coating. To ensure deep dye penetration into these dense nanofibers meshes, advanced processing technologies like ultrasonic-assisted dyeing are employed, utilizing cavitation effects to preserve fiber integrity. Furthermore, precise control of parameters, such as maintaining a temperature of approximately 80°C, is essential to open the fiber microstructure while preventing the degradation of mechanical properties. By integrating these surface modifications with advanced techniques, it is possible to develop functionalized PAN nonwoven textiles with good color fastness and scalable application potential. Keywords: Polyacrylonitrile (PAN), Nanofibers, Nitrile Hydrolysis, Cationic Dyeing, Surface Activation