Molecular dynamics simulation study of the effect of a strong electric field on the structure of a poly(oxyethylene) chain in explicit solvents

Abstract

Molecular dynamics simulations are carried out to investigate the structure of a single poly(oxyethylene) (POE) chain in aqueous and methanolic solutions in a strong external electric field. The conformational changes of the polymer chain induced by the strong external electric field are monitored by measuring the radius of gyration, the components of the gyration tensor, the end-to-end distance, dihedral angle distribution, and the helical content. The isotropic coil size measures, i.e., the radius of gyration and the end-to-end distance mostly decrease with growing intensity of the electric field except a small increase occurring between 0 and 1 V/nm in water. Therefore, in most cases the field compresses the polymer coil. Nevertheless, the deformation is anisotropic, leading to an average spheroid which is prolate in water (again with the exception of fields less or equal to 1 V/nm) and oblate in methanol. Analysis of dihedrals suggests that POE chain’s partially helical structure is promoted at electric fields above 1 V/nm. Changes caused by the strong external electric field in the solvent–solvent and solvent–polymer hydrogen-bonding structure are monitored by measuring the number of hydrogen bonds, their strength, and the volume of the bonding region. Results show non-trivial, solvent-specific effects, which are yet to be fully understood.