Thermally Induced Cross-Linking and Degradation Reactions of Benzocyclobutene-Based Polymers

Abstract

We describe the use of MALDI-TOF mass spectrometry and collision-induced dissociation (CID) fragmentation techniques to examine the thermally induced cross-linking chemistry of dibenzocyclobutene (BCB)2–resorcinol-based materials. The overall goal was to gain a better understanding of benzocyclobutene ring-opening and the subsequent Diels–Alder cycloaddition reactions, which could assist in troubleshooting problems associated with unwanted side-product formation in these materials. Experimental results indicate that relative changes in average molecular mass (e.g., Mn) and signature side-product formation can be used to predict the optimum curing temperature used for cross-linking/polymerization. CID fragmentation studies identified two low kinetic energy degradation pathways for the BCB2–resorcinol-based oligomers examined in this study: (1) ether bond cleavage with an associated 1,3-hydrogen transfer and (2) transannular bond cleavage across the cyclooctadiene linkage. This information was used to develop a general fragmentation model for BCB2–resorcinol-based materials to predict their degradation products and verify their chemical connectivity.