A systematic investigation of the ring size effects on the free radical ring‐opening polymerization (rROP) of cyclic ketene acetal (CKA) using both experimental and theoretical approach

ABSTRACT Radical ring‐opening polymerization (rROP) reaction of cyclic ketene acetals (CKA) is an interesting route to biodegradable polymers. Contrary to their tremendous potential, fundamental understanding of their reaction kinetics and thermodynamics is still limited. We present experimental and theoretical investigations for rROP reactions of CKA to systematically elucidate the effects of monomer ring sizes on the homopolymerization. We aim to provide insights on the structural‐reactivity relationship of CKA by studying the thermodynamics and kinetics of the forward ring‐opening propagation reactions and key side reactions, namely ring‐retained propagation and radical back‐biting reaction leading to branching. Experimental results show that for the CKA with smaller ring sizes, significant amount of ring‐retained side products are formed when up to 90% of the monomers are converted. However, for the larger ring sizes (7 and 8 membered), almost complete ring‐opening polymerization with