Charge symmetry breaking in neutral polyzwitterions

Response of polar and neutral monomers in macromolecules to an electric field in their crowded aqueous solutions remains as an unchartered area of research, in contrast with well understood behavior of ionized groups. Wondering whether such monomers impart merely frictional resistance or cooperate with the other ionic groups in their electrophoretic mobility, we investigate single-molecule electrophoresis of a couple of neutral polyzwitterions which have charge-neutrality with strong acidic group and permanent positive charge within their repeat units. Combining experiments and theory, we study the roles of dipole orientation of zwiterionic monomers and salt identity. Here, we report that charge-neutral polyzwitterions exhibit mobility with rectification in their direction of movement because of charge symmetry breaking arising from differential counterion bindings due to gradients in the local dielectric constant around chain backbone, and thus opening a new avenue to understand dipolar polymers of broad interest and applications.