Abstract:

The ring-opening polymerization process of ethylene oxide as initiated by sodium methoxide was studied using the density functional theory (DFT)/Dmol3method. Various steps of this polymerization reaction were analyzed by frontier orbital theory. For the chain initialization step, no energy barrier was apparent for the exothermic reaction and the energy released was 92.560 kJ·mol -1. The chain growth step needed to overcome a 100.951 kJ·mol-1 energy barrier. Frontier orbitals of chain growth species and those of ethylene oxide were similar and symmetric, so the ring-opening polymerization of ethylene oxide could occur smoothly. When adding a protonic acid, such as oxalic acid or phosphoric acid into the system, the polymerization chain growth would be terminated immediately. In addition, transition states were analyzed and confirmed while a potential energy diagram versus reaction coordinates was compiled for this polymerization process.

Key words: Ethylene oxide, Analysis of polymerization steps, Frontier orbital, Transition state, Density functionary theory