Cross-Linking Mechanism\nof the Butadiene–Maleic\nAnhydride Copolymerization

With the expansion of ethylene production, butadiene\nwill face\na crisis of overcapacity by 2025. Converting it into high-value functional\ncopolymers is more desirable. A butadiene–maleic anhydride\ncopolymer is an amphiphilic alternating copolymer with potential applications\nin adhesives, emulsifiers, composite compatibilizers, and so forth.\nHowever, the unpredictable cross-linking reaction limits its research\nand industrial production. In this paper, the structural differences\nbetween linear and cross-linked copolymers are identified by Raman\nand nuclear magnetic resonance spectroscopy, and the transformation\nprocess from linear to cross-linked copolymers is investigated. We\ndemonstrate that the cross-linking process is caused by the 1,2-unit\nvinyl (>2%) at a high copolymer concentration of 500 mg/mL. We\nreveal\nthe cross-linking mechanism and identify the critical factors in this\nprocess. This work provides a theoretical basis for guiding the production\nof conjugated diolefin–maleic anhydride copolymers with a controllable\ngel fraction and improving the efficient utilization of butadiene.