Low‐Energy Driven Ring‐Opening Behavior of Benzocyclobutene Derivatives

Abstract

Comprehensive SummaryIt's urgent to develop benzocyclobutene (BCB)‐based polymers with low curing temperature for temperature‐sensitive applications such as liquid crystal displays (LCDs) and flexible electronics. Herein, the effect of substituents on the ring‐opening behavior of BCB derivatives was investigated. The ring‐opening activation energy barriers (ΔGA) of BCB derivatives with one or two substituents on the four‐membered alkyl ring were systematically calculated using the B3LYP function. Both mono‐ and di‐substituted BCBs adopted the conrotatory ring‐opening process, obeying the Woodward‐Hoffmann's Rules upon heating. The mono‐/di‐substituted BCBs exhibited 8.2%—69% lower ΔGA compared with BCB, attributed to the electronic effects of the substituents. Disubstituted BCBs with both electron‐donating and electron‐withdrawing groups, e.g., 1‐NH2‐8‐NO2‐BCB, demonstrated the lowest ΔGA. In addition, BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules, and their ring‐opening temperature can be decreased by 20 °C compared to the unsubstituted one, also consistent with our calculation results. This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next‐generation BCB functional packaging materials with low ring‐opening temperature.