<scp>PA6</scp> Microspheres Synthesized by In Situ Anionic Phase Transfer Polymerization for Electromagnetic Shielding

ABSTRACT Polyamide 6 (PA6) microspheres are typically prepared via phase transfer during in situ anionic polymerization of caprolactam (CL) induced by single hydrophilic or hydrophobic polymers. However, systematic studies on the influence of amphiphilic polymers on PA6 microsphere morphology are lacking. In this study, amphiphilic PS‐b‐PEG‐b‐PS block copolymers were synthesized by electron transfer activated regenerated atomic transfer radical polymerization (AGET ATRP). Polyethylene glycol (PEG), as a typical hydrophilic polymer, exhibits significant influence on interfacial properties and phase separation behavior through its molecular weight variations. In pure PEG systems, PA6 microspheres transformed from continuous phase (PEG2K) to isolated spherical structures (PEG6K). After introducing polystyrene (PS) segments onto PEG chains, PA6/PS‐b‐PEG‐b‐PS blends formed with significantly increased microsphere size due to reduced interfacial tension. Through thermodynamic and kinetic analysis, we revealed the microstructural regulatory mechanism of interfacial tension and compatibility competition. PA6 microspheres were further developed into PA6@Ni magnetic microspheres and combined with conductive silver nanowires (AgNWs) to construct magnetic–electric gradient AgNWs/PA6@Ni/CNF‐H (CPNA‐H) composite films. The CPNA‐H composite films achieved a total shielding effectiveness of 62.85 dB in the X‐band (8.2–12.4 GHz), 13.9% higher than non‐magnetic AgNWs/CNF films, providing theoretical guidance for polymer blends microstructural design and lightweight electromagnetic shielding materials development.