Molecular insights into an electrolytic polymer, polyethylene imine

Our comprehensive analysis, which involved a range of scientific disciplines, including density functional theory (DFT) calculations, broadband dielectric spectroscopy (BDS), and Fourier transform infrared (FTIR) spectroscopy, has revealed crucial insights into the structural, electronic, and charge transport properties of polyethyleneimine (PEI). This interdisciplinary approach enriches our understanding of PEI and engages a wide range of scientific professionals. DFT calculations provided detailed insights into PEI's structural and electronic properties, unveiling its stable, low-energy configuration. BDS was employed to investigate PEI's charge transport and molecular rotational properties. The ion hopping mechanism in PEI is facilitated by reorganizing multiple amine groups at high temperatures, with an activation energy of 0.358 eV and a maximum DC conductivity of 10 −9 S/m. Two distinct relaxations were identified: a slower α-relaxation associated with the molecular rotation of more significant polymer segments and a faster Johari –Goldstein β relaxation. The α process is due to the cooperative motion of the molecules, which is associated with glass transition, and the glass transition temperature T g was calculated to be 212 K with an activation energy 222 kJ/mol, the T g was in good agreement with the T g obtained from the DSC. FTIR spectroscopy and molecular dynamics simulation explored PEI's water solubility. Shifts in amine stretching peaks and the broadening of the O–H stretching peak indicated hydrogen bond formation, enhancing PEI's solubility by disrupting its intramolecular arrangement. This hydrogen bonding network, involving interactions between oxygen atoms in water and hydrogen atoms in the amine groups, was further corroborated by changes in peak intensities and the appearance of new shoulders in the FTIR spectra. Hence, PEI's stable configuration, effective ion hopping mechanism, and robust hydrogen bonding network contribute to its excellent conductivity and solubility. These properties underscore PEI's suitability for various advanced applications, including high-performance electrolytic devices and aqueous-based systems, and provide a pathway for designing and optimizing PEI-based materials for cutting-edge technological applications. • Interdisciplinary study of PEI using DFT, BDS, and FTIR spectroscopy. • The α-relaxation in PEI has been identified for the first time. • The ion hopping mechanism in PEI, with an activation energy of 0.358 eV, drives conductivity. • The study reveals the hydrogen bonding network in PEI, enhancing its water solubility for industry. • The findings are key to understanding PEI's properties, supporting its use in industry and drug delivery.