Multifunctional Maleic Anhydride–Styrene–N‐Carboxyphenylmaleimide Terpolymers: Synthesis, Molecular Design, Thermal Robustness, and Synergistic Antioxidant–Antimicrobial Activity

ABSTRACT

Novel multifunctional maleic anhydride–styrene–N‐carboxyphenylmaleimide (MA–St–CPMI) terpolymers containing ortho ‐, meta ‐, and para ‐carboxyphenylmaleimide units were synthesized by free‐radical solution terpolymerization to investigate the influence of positional isomerism on their physicochemical and biological properties. The chemical structures were characterized by FTIR and UV–Vis spectroscopy, while molecular‐weight characteristics, terpolymerization kinetics, thermal behavior, rheological properties, antimicrobial activity, and antioxidant performance were systematically evaluated. Kinetic analysis using the modified Alfrey–Goldfinger and Kelen–Tüdös methods showed that CPMI incorporation increased in the order o ‐ <  m ‐ <  p ‐CPMI, indicating enhanced reactivity of the para ‐substituted monomer. The MA–St– p ‐CPMI terpolymer exhibited the highest intrinsic viscosity and antioxidant activity among the three positional isomers. Among the thermally characterized samples, the p ‐CPMI‐containing terpolymer also showed the higher apparent DTA‐based glass‐transition temperature and residual char yield, indicating enhanced thermal performance. Rheological measurements revealed typical shear‐thinning behavior, whereas antimicrobial testing showed activity against representative Gram‐positive and Gram‐negative bacteria and Candida albicans , with the ortho ‐substituted terpolymer displaying the strongest antibacterial activity and the meta ‐substituted analogue the highest antifungal activity. These findings demonstrate that positional isomerism provides an effective strategy for tailoring the structure–property relationships of MA–St–CPMI terpolymers and highlights their potential as multifunctional materials for polymer stabilization, protective coatings, adhesive systems, and functional packaging.