Post-Polymerization Modification of CO₂-Based Polycarbonate Based on Borate Ester Bond

Carbon dioxide (CO₂)-based polycarbonates represent a class of green and sustainable polymers that have attracted considerable attention due to their CO₂ utilization and biodegradability. However, as an emerging polymer material, research on their modification and applications remains in the exploratory stage. In this study, CO₂, propylene oxide (PO), and allyl glycidyl ether (AGE) were used as raw materials to synthesize CO₂-based polycarbonate (PAGC) bearing pendant double bonds through terpolymerization. The structure and composition of the target polymer were confirmed by nuclear magnetic resonance spectroscopy (¹H-NMR), Fourier transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). Post-polymerization modification was achieved by introducing 2,2'-(1,4-phenylene)-bis(4-mercapto-1,3,2-dioxaborolane) (BDB) into PAGC side-chains through UV-initiated thiol-ene click reaction, yielding a series of PAGC-BDB modified materials. Experimental results demonstrated that the crosslinked network structure formed by the click reaction significantly enhanced the material properties. The tensile strength of the modified material increased from 32.4 MPa to 51.6 MPa. Differential scanning calorimetry (DSC) analysis revealed an increase in glass transition temperature (T_g) from 24.7 ℃ to 38.5 ℃, and thermal stability was also effectively enhanced. Further investigation showed that the material exhibited excellent self-healing properties and recyclability, benefiting from the dynamic reversibility of boronic ester bonds. After hot-pressing at 160 ℃ and 5 MPa for 1 h, the recycled material retained 95% of its initial tensile strength. These results collectively demonstrate the efficacy of this post-polymerization modification strategy in improving the overall performance of PAGC, thereby broadening its potential applications.