Free radical copolymerization of acrylic acid and 2-ethoxyethyl methacrylate: synthesis, mechanism, characterization, reactivity ratios, microstructure and Potential applications

This study reports the free radical copolymerization of acrylic acid (AA) and 2-ethoxyethyl methacrylate (2-EOEMA) using benzoyl peroxide as the initiator in acetone under a nitrogen atmosphere. The copolymers were synthesized at low conversion (~15%) to facilitate accurate determination of monomer reactivity ratios. The copolymerization mechanism was investigated and confirmed through FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy, revealing the successful incorporation of both monomers. Solubility studies demonstrated that increasing the AA content enhances water solubility, making the copolymers suitable for surface-active and biomedical applications. Reactivity ratios were calculated using the Fineman-Ross (F-R) and Kelen-Tüdös (K-T) methods based on FT-IR spectral data, yielding average values of r₁ (AA) = 0.7391 and r₂ (2-EOEMA) = 0.2242, indicating a random copolymerization tendency (r₁•r₂ = 0.1652). Azeotropic composition analysis and sequence distribution calculations further supported the random nature of the copolymer, with 2-EOEMA showing higher reactivity. The copolymer microstructure was also analyzed by evaluating mean sequence lengths and monomer distribution along the polymer chain. These findings suggest that AA/2-EOEMA copolymers, due to their tunable solubility and monomer composition, hold promise for applications in drug delivery, coatings, and as surface-active agents.