The competition between radical copolymerization and charge separation of cyclic ketene acetals and electron-deficient olefins

Cyclic ketene acetals (CKAs) possess unique features in two aspects. On one hand, after the addition of a radical on the alkene, CKAs can undergo ring-opening via radical rearrangement, enabling polyester preparation based on chain-growth polymerization. On the other hand, the alkene connected with two electron-donating oxygens in a strained form exhibit unique reactivities, resulting in complex reactions in the presence of electron deficient compounds. In this investigation, fundamental studies on CKA radical ring-opening polymerization and charge-mediated reactions were performed. Alternating copolymers of CKA and maleimides, or maleates, were prepared and characterized. Quantum chemistry modeling from the perspectives of reaction kinetics and thermodynamics enabled an in-depth mechanistic study on the side reactions between CKA and maleic anhydride or itaconic anhydride, inspiring the techniques to minimize those side reactions in competition with radical copolymerization. After purifying the anhydride monomers with sublimation, the copolymerization with CKA successfully occurred. The anhydride containing polyester structures with an alternating sequence were confirmed with comprehensive characterizations. Facile post-functionalization with an alcohol was performed, resulting in carboxylate containing polyesters. image