Preparation of Sulfonate-Functionalized Cross-Linked Polysulfone-Benzoxazine/Calix[4]Arene Copolymer for Specific Adsorption of Methylene Blue

The novel cross-linked copolymer (BPSU-C4A-SPS) was synthesized by the copolymerization of benzoxazine-functionalized polysulfone (BPSU), calix[4]arene (C4A), and sodium 4-hydroxybenzenesulfonate (SPS). The material exhibited high thermal stability with a glass transition temperature ( T g ) of 285°C and a 5% weight loss temperature ( T d5 ) of 347°C, and enhanced hydrophilicity with a water contact angle of 76.5°. Moreover, adsorption studies on MB demonstrated that BPSU-C4A-SPS possesses a higher adsorption capacity than the benzoxazine-functionalized polysulfone homopolymer (BPSU-a) and the benzoxazine-functionalized polysulfone-calix[4]arene copolymer (BPSU-C4A). Adsorption followed the Freundlich isotherm and pseudo-second-order kinetics best describes the adsorption process of BPSU-C4A-SPS to MB, indicating multilayer chemisorption driven by electrostatic interactions and π-π stacking. This work provides a scalable strategy for designing stable adsorbents with synergistic effects, suitable for industrial wastewater treatment.