Cationic polymers are macromolecules bearing positively charged groups, usually quaternary ammonium or protonated amine functions, either along the backbone or on side chains ^[1]. The charge density, set by the fraction of ionisable monomers and by the degree of protonation at a given pH, governs how the chain binds to anionic surfaces of nucleic acids or cell membranes ^[2]. Because the charge is distributed over many repeat units, the polymer binds multivalently and condenses counter-charged macromolecules into complexes, an effect not available to a monovalent cation ^[3]. They differ from anionic and neutral polymers in that electrostatic attraction, rather than hydrogen bonding or hydrophobic association, dominates their interaction with dissolved polyelectrolytes ^[1].