Conformational Behavior of a Single Polymer Chain with Polar Groups under Stretching in аn Electric Field

The conformational behavior of a single polymer chain with polar groups is studied using molecular dynamics simulations under the combined action of a mechanical stretching force and an external electric field. The polar groups are uniformly distributed along the chain and modeled as dipolar units composed of two oppositely charged beads that are covalently bonded together. One of the beads is incorporated into the backbone chain, while the other forms a side group. Special attention is paid to the chain behavior in low-polarity environments, where the polymer forms a polyelectrolyte globule. It is demonstrated that an external electric field aligned with the stretching force F promotes chain extension at small values of F. At higher extensions, however, the application of the field leads to partial contraction of the chain due to electrostatic attraction between dipoles, which tend to align along the field direction and form linear aggregates. The structure of ionic aggregates and the degree of orientational ordering of dipoles are analyzed as functions of solvent polarity, the field strength, and the relative orientation of the electric field and the stretching force.