Electrostatic interactions are instrumental in determining the structure and function of living organisms, biopolymers and drug delivery systems. Charged macromolecules can self-assemble and aggregate into compact intermolecular complexes.
This ability of oppositely charged polymers to form finite size complexes determines their biological function, which for example is important in gene transfection and compactization of DNA, that provide promising alternatives to viral vectors. Such macromolecular systems, where electrostatic forces are usually stronger than van der Waals or hydrogen bonds, exhibit rich behavior and structural variability. The structures formed by opposite charges are usually more stable than neutral block copolymers micelles dissociating upon dilution or slight change in the external conditions.
The concept of stabilization of intermolecular complexes by interaction of oppositely charged polymers is realized in interpolyelectrolyte or polyion complexes (PIC) and polyion complex micelles (PIC micelles) that can be used for drug delivery.