Charge symmetry breaking in neutral polyzwitterions

Area of Science:

• Polymer physics
• Electrokinetic phenomena
• Solution chemistry

Background:

• The electrophoretic behavior of ionized groups in macromolecules is well-understood.
• The response of neutral or polar monomers in macromolecules to electric fields in aqueous solutions is largely unstudied.
• It remains unclear if neutral monomers offer only frictional resistance or actively contribute to electrophoretic mobility.

Purpose of the Study:

• To investigate the electrophoretic mobility of neutral polyzwitterions in aqueous solutions.
• To explore the influence of monomer dipole orientation and salt identity on polymer movement.
• To elucidate the mechanisms behind the response of charge-neutral polymers to electric fields.

Main Methods:

• Single-molecule electrophoresis experiments were conducted.
• Theoretical modeling was employed to analyze the experimental data.
• The study focused on polyzwitterions with charge-neutral repeat units containing acidic and positive charges.

Main Results:

• Charge-neutral polyzwitterions demonstrated rectified mobility, moving preferentially in one direction.
• Charge symmetry breaking was identified as the cause of rectified motion.
• Differential counterion binding, influenced by local dielectric constant gradients, was found to be responsible for charge symmetry breaking.

Conclusions:

• Neutral polyzwitterions can exhibit directed movement in electric fields, contrary to simple frictional resistance.
• The findings reveal a novel mechanism for controlling polymer motion via intrinsic charge distribution and counterion interactions.
• This research opens new avenues for understanding and utilizing dipolar polymers in various applications.