This special topic highlights recent advances in experiments, theory, and coarse-grained modeling on charged macromolecular systems involving synthetic and biological polymers and membranes. The behaviors of the charged systems are very complex and are qualitatively different from those of uncharged polymers. The results presented in this special topic provide deep insights into the fundamentals of how the coupling between the long-ranged electrostatic and topological correlations of charged macromolecules controls their conformations, assembly, dynamics, and transport. There are many insights into the creation and design of new materials based on ionic interactions.

Charged macromolecules possess a broad range of structural and functional properties and are ubiquitous in the biological world as well as water-based materials in the health care industry and biotechnology. Aqueous solutions containing charged macromolecules, both synthetic and biological, exhibit many unusual properties unseen in systems of uncharged molecules. The main attribute of systems of charged macromolecules is that all molecules are cooperatively correlated both topologically and electrostatically in a medium of highly polarizable solvent and small electrolyte ions. The various inevitable long-ranged strong correlations among all constituents of the charged systems and the necessary use of numerous variables in experiments on these systems continue to present immense challenges in achieving a predictive capability in this field. While a fundamental understanding of the behavior of charged macromolecules remains as one of the major challenges in polymer science, soft matter, and biological science, many advances have recently been achieved.

The thirty-six articles in this special topic of The Journal of Chemical Physics highlight the recent advances on the physical principles behind the physics of charged macromolecules based on experiments, simulations, and theory. This wonderful collection of papers covers almost all aspects of charged macromolecules which include conformations of isolated macromolecules and their charge regularization, polarizability of the medium, specific ion effects, multi-valency, mobility of macromolecules of different chemical architectures, intrinsically disordered proteins, crowded solutions, adsorption to charged brushes, dendrimers and membranes, self-assembly of proteins and coacervates, morphology of charged block copolymers, kinetic pathways of complexation among macromolecules, critical phenomena, and flow effects. The articles in this collection are of the highest caliber reflecting the current state of the field in the world.

We are delighted to have received such an exciting and stimulating collection of papers at the cutting edge of the subject. We are confident that this collection will stimulate further deep advances in the field of charged macromolecules, which is one of the most challenging subjects in room temperature physics. We hope this collection is both useful and enjoyable.