Sc(OTf) ₃ -Mediated Alternating Ethylene-Methyl Acrylate Copolymers with over 95% Mechanical Retention in Hot Oil via Sequence Control under Mild Conditions

High methyl acrylate (MA) content coupled with a well-defined alternating MA-ethylene (MA-E) sequence is essential for high-performance ethylene-methyl acrylate (MA-E) elastomers with superior heat and oil resistance. However, achieving this structure is challenging with coordination or conventional radical polymerization methods. This work presents a feasible synthesis of MA-E copolymers with exceptionally high MA content (exceeding 50%) via scandium trifluoromethanesulfonate (Sc(OTf)3)-mediated radical copolymerization under mild conditions. Through systematic parameter optimization, we obtained copolymers with high molecular weight (Mn > 5.0 × 104 g/mol) and a predominantly alternating sequence. Incorporating maleic anhydride introduced cross-linking sites while maintaining the primary alternating structure, as confirmed by 13C NMR analysis. The cross-linked elastomer exhibited exceptional stability, showing only minimal changes in mass (0.83% increase), tensile strength (2.95% loss), and elongation at break (6.20% reduction) after 72 h of aging in paraffinic mineral oil at 100 °C. This study provides a practical method for synthesizing MA-rich MA-E copolymers with well-defined alternating sequences under mild conditions.