Slow Initiation Mechanism and Accelerated Kinetic Monte Carlo Simulation for Quantifying Metallocene-Catalyzed Ethylene–Norbornene Copolymerization Reaction Rates and Product Microstructure

Abstract A reaction kinetic model involving a mechanism controlled by chain initiation and catalyst deactivation as well as an accelerated kinetic Monte Carlo (kMC) method predicting copolymer microblocks were developed for the metallocene-catalyzed ethylene–norbornene copolymerization. The outcomes demonstrated excellent agreement with the published experimental data and revealed that the vast majority of polymer chains are formed by initiated ethylene. By combining code optimization with the Numba module, our kMC simulation calculated the intricate copolymer microstructure without conventional quasi-steady-state assumption while optimizing system size to balance computational efficiency against the smoothness of concentration profiles. Found by a systematic sensitivity analysis for all rate constants, the key reactions and their rate constants were finely tuned using a particle swarm optimization (PSO) framework. The integrated kMC-PSO approach effectively captured macroscopic experimental metrics including norbornene conversion and molecular weights. Furthermore, while the model accurately reflects the overall composition, discrepancies in norbornene-containing triad distributions demonstrate the inherent physical boundaries of classical penultimate models in capturing complex stereochemical sequence effects under high feed ratios, providing critical mechanistic insights for advanced copolymerization modeling.