Conformation and ionization behavior of charge-regulating polyelectrolyte brushes in a poor solvent

Understanding the structural response of weak polyelectrolyte brushes upon external stimuli is crucial for their applications ranging from modifying surface properties to the development of smart and intelligent materials. In this work, LAMMPS-based coarse-grained molecular dynamics simulations were carried out to investigate the conformation and ionization behavior of charge-regulating polyelectrolyte brushes in poor solvent conditions. The results show that, while the thickness of a sparse polyelectrolyte brush shows a similar behavior as that of a single chain, namely a monotonic change as a function of solvent quality and solution pH, dense polyelectrolyte brush exhibits more complex behavior. An unexpected re-expansion is observed when the solvent quality is further reduced, especially in the case of high pH.