Recent Advances in Addition Copolymerization of Cyclobutenes

Abstract

Cyclobutene is a highly strained cyclic olefin that can undergo addition polymerization while retaining its four-membered ring as a cyclobutane unit in the polymer backbone. However, the strained structure and distinct reactivity of cyclobutene also make it susceptible to competing pathways, including ring opening and olefin isomerization, which pose significant challenges to chain propagation. Therefore, it is crucial to develop efficient catalytic polymerization systems capable of suppressing these side reactions while enabling selective addition polymerization of cyclobutene. Recent advances in catalytic coordination/insertion and radical copolymerization have enabled the incorporation of polar and rigid cyclobutane units into polymer backbones with tunable content, thereby facilitating the effective modulation of material properties. Furthermore, these units are susceptible to undergoing force-triggered cycloreversion upon mechanochemical activation, introducing degradable moieties into the polymer backbone. Continued progress in catalyst design and polymerization strategies is expected to further expand the scope of cyclobutene addition polymerization, paving the way toward high-performance polymers with on-demand degradability.