A Polymer Backbone Editing Strategy for Property Enhancement

The properties of polymers are closely related to their microstructure, particularly their backbone architecture. Polymer backbone editing (PBE) transforms the backbone architecture through postpolymerization modification. However, the utilization of this strategy to alter polymer material properties has remained largely unexplored. In this study, a PBE strategy was employed to modify the backbone architecture of a polynorbornene (PNB) to enhance its comprehensive material properties. This PBE strategy involved two steps, the epoxidation of PNB and a ring expansion reaction of the resulting epoxidized polynorbornene (EPNB), which achieved high efficiency and selectivity without causing polymer degradation or cross-linking. The ring expansion reaction mechanism was investigated experimentally and via density functional theory (DFT) calculations. The results revealed that a Lewis acid catalyzed the activation of the C-O bonds. This reaction generated a rigid main-chain architecture with bridged ring units with significantly improved heat resistance (T_g = 233 °C) and mechanical properties. Due to the introduction of polar oxygen-containing functional groups, the PBE products exhibited greater hydrophilicity and adhesion to inorganic substrates than PNB with a hydrocarbon chain structure. This PBE strategy provides a promising approach to improving the material properties of polymers after their formation.