<div> Here, the quartz crystal microbalance with dissipation monitoring (QCM-D) is employed to explore the interaction of the various free oxidant species with condensed PA model membranes in order to improve our understanding of how the interaction with these species affects rates of membrane chlorination and alter membrane structure. Molecular-scale mass uptake and changes in the dissipative nature of the of the model membranes as measured by the QCM is correlated to performance changes in interfacially polymerized PA reverse osmosis (RO) membranes. Leveraging newly gained insights from these measured interactions, new strategies are explored to improve flux and chlorine resistance using novel membrane structure and chemistry.<br></div>