Interfacial polymerization is widely used today for the production Of Ultrathin Films for encapsulation, chemical separations, and desalination. Polyamide films, in particular, are employed in manufacturing of reverse osmosis and nanofiltration membranes, While these materials show excellent salt. rejection, they have rather low water permeability, both properties that apparently stein from the rigid cross-linked structure. An increasing amount of experimental research on membranes of different chemistries and membrane characterization Suggests the importance of other factors (such as unreacted functional groups and Surface roughness) in determining membrane performance. We developed a molecular simulation model to qualitatively Study the effects of various Synthesis conditions on membrane performance, in terms of its estimated porosity and permeability. The model is of an interfacial aggregation process of two types of functional monomers. Film growth with time and Structural characteristics of the Final film are compared with predictions of existing theories and experimental observations.