Synthesis and Comparative Investigation of Ortho-, Meta-, and Para-Carboxyphenylmaleimide–Styrene Copolymers

The copolymerization of biologically active N-(carboxyphenyl)maleimides with styrene was systematically investigated to elucidate the effect of positional isomerism (ortho-, meta-, and para-) on monomer reactivity and copolymer properties. Reactivity ratios (r1, r2) were determined using the Fineman–Ross method, and Q–e parameters were evaluated within the Alfrey–Price framework, revealing distinct electronic effects governing copolymerization behavior. Increasing the maleimide fraction in the feed resulted in decreased copolymer yield, intrinsic viscosity, molecular weight, and glass transition temperature, while all copolymers remained styrene-rich, indicating preferential styrene propagation. Comprehensive structural characterization (NMR, FTIR, and UV–Vis) confirmed successful incorporation of both monomer units. Rheological analysis demonstrated a clear viscosity trend (ortho > meta > para), highlighting the influence of substituent position on chain interactions and macromolecular architecture. Thermal analysis (TGA/DTA) showed good thermal stability up to 250–300 °C. Notably, the copolymers exhibited significant antibacterial and antifungal activity, with maximum inhibition observed against Candida albicans. This study establishes a direct correlation between substituent position and structure–property relationships, providing new insights for the rational design of functional styrenic copolymers with potential applications in antimicrobial and biomedical materials.