Uncovering the Screening-Enhanced Behavior of Poly(hexamethylene biguanide) Hydrochloride in Overcoming Charge Screening Limitations

Conventional ionic polymers can effectively adsorb small molecules of opposite charges, but their applications are limited by the consensus that inorganic salt ions typically screen electrostatic binding between them. This weakness results in significant deterioration in the performance of electrostatic-dominant chemical processes. Herein, we reported that cationic poly(hexamethylene biguanide) (PHMB) exhibits an exceptional screening-enhanced effect, enabling its flocculation performance to be enhanced by salt ions rather than weakened by them. Flocculation experiments and theoretical simulations revealed that the superior performance of PHMB is attributed to its abundant biguanide groups, enabling screening-enhanced behavior through stable PHMB-dye adsorption, increased same-segment stacking, and a moderately enhanced hydrophobic effect in high-salt environments. This study may lay a solid foundation for developing screening-enhanced materials with the powerful capabilities of overcoming charge screening limitations for specific application scenarios.