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.