Vibrational Assignments for High Molecular Weight Linear Polyethylenimine (LPEI) Based on Monomeric and Tetrameric Model Compounds

Polyethylenimine-based systems provide an interesting alternative to poly(ethylene oxide)-based systems for investigation of polymer electrolyte properties. Vibrational spectra may be used to infer conformations of polyethylenimine, but unambiguous assignments of IR and Raman bands must first be available. Hybrid Hartree−Fock/density functional methods were used to calculate the vibrational frequencies, modes, and infrared intensities for DMEDA (a monomeric model for LPEI) and a tetrameric model for LPEI. These results were then used to help assign the experimentally observed bands in the infrared and Raman spectra of LPEI.