Quantitative insights into electrostatics and structure of polymer brushes from microslit electrokinetic experiments and advanced modelling of interfacial electrohydrodynamics

Polymer brushes are widely applied to modify and functionalize material surfaces.Fundamental understanding of polymer brush properties was achieved with the development of polymer theories and by the application of physico-chemical methods.The development of electrohydrodynamic formalisms for soft surfaces enabled major progress in the quantitative interpretation of streaming current and surface conductivity data collected for polymer brushes.In this paper, we review the basics of the methodology adopted for the analysis of interfacial charging and structure of polymer brushes, and illustrative examples of practical interest are discussed.In particular, we demonstrate how the combination of self-consistent field (SCF) and soft surface electrokinetic theories using Poisson-Boltzmann (PB) formulations allow the evaluation of the segment density distribution within poly(ethylene oxide) (PEO) brushes beyond the resolution limits of neutron reflectivity.The application of the methodology for the analysis of the charge, structure, and pairing with chaotropic anions is illustrated for strong cationic poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMETAC) brushes.Finally, we report refinements of the PB theory account for ion hydration, ion pairing, and dielectric decrement in brushes and we present an example of glycosaminoglycan (GAG) brushes where those effects are significant.