Effects of Salt and Molecular Structure on the Solution Properties of Charged Functional Polyacrylamides

The solution properties of charged functional polyacrylamides in saline environments are critical for their applications, yet a quantitative understanding of the effect of salt and molecular structure on their properties remains elusive. Herein, we systematically investigate the solution properties of negatively charged functional polyacrylamide, P(AM- co -AMPS), in semidilute solutions using a scaling approach, focusing on the roles of salt and AMPS molar fractions ( F S ). The result reveals that the excluded volume Ve decreases with increasing salt concentration and ionic valence. Concurrently, both Kuhn length b and Ve increase with F S in near-θ solvent conditions, scaling as b ∼ F S 0.45 and Ve ∼ F S 0.9 . Molecular simulations uncover the underlying mechanism, suggesting that the chain conformation and solution properties are governed by the balance between the competition of cation–polymer electrostatic interactions and the steric hindrance of AMPS units, where the former promotes chain contraction by weakening polymer–solvent interactions and the latter favors chain extension. These findings provide molecular-level insight into the solution properties of charged functional polyacrylamides in saline environments and establish a theoretical basis for designing salt-resistant functional polymers.