Abstract
We focused our study on the hydrated polyethylenimine (PEI) crystals which are characterized by the presence of 0.5, 1.5 or 2 water molecules per ethylenimine monomer unit. We propose a theoretical study in the framework of periodic linear combination of atomic orbitals (LCAO) using different Hamiltonians based on density functional theory (DFT) and hybrid Hartree–Fock (HF) – DFT level of theory. Once hydrogen atoms added when missing and redundant atoms withdrawn in the PEI structures, ab initio calculations yielded relaxed geometries at the ground state. The closest structural parameters to the experimental values are observed for hybrid Hamiltonians and the use of the 6-31++G∗ basis set reduces this difference. We provide the IR vibration modes at the Γ point, with assignments of the bands. The electronic study reveals that these PEI hydrates have an insulating character with a quasi constant band gap whatever the number of water molecules. From the projected density of states (PDOS), we have found that the nitrogen orbital has the major contribution to the valence band, while the conduction band is mainly constructed from hydrogen bondings.
Highlights
PEI is widely used in different industrial, agricultural and biological applications [1,2,3]
As the LDA functional approximates the energy of the true density by the energy of a local constant density, it fails in situations where the density undergoes rapid changes such as PEI hydrates
An improvement was made by considering the gradient of the electron density, the so-called generalized gradient approximation (GGA) [19]
Summary
PEI is widely used in different industrial, agricultural and biological applications [1,2,3]. Due to its high cationic state and its ability to complexe DNA, the linear form of PEI is very attractive for gene transfection. This polymer takes many forms: linear or branched, hydrated or anhydrous, solid or liquid depending on its molecular weight and its synthesis way: organic, electrochemical [4,5,6,7,8]. Water molecules can unroll the doubled stranded PEI structure when anhydrous leading to linear zigzag polymer chains. We propose to study the effect of the presence of water molecules and additional intermolecular interactions on the infrared spectra and electronic properties of the hydrate complexes. PEI hydrates at different level of theory using two different basis sets: 6-21G and 6-31++G* [10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
