M.Sc Thesis

M.Sc StudentNadler Rachely
SubjectMolecular Simulation of polyamide Synthesis by Interfacial
DepartmentDepartment of Chemical Engineering
Supervisor ASSOCIATE PROF. Simcha Srebnik
Full Thesis textFull thesis text - English Version


Interfacial polymerization is a highly used method, especially in manufacturing thin film composites membranes used for desalination and filtration by reverse osmosis

and ultra-filtration. The reaction in interfacial polymerization takes place at the interface of an organic and aqueous phase system. Experimental studies of the reaction kinetics and barrier layer structure of the film are difficult because of the fast reaction rate and small film thickness. In this study we simulate the formation of polyamide film from trimesoyl chloride and phenylene diamine using a modified cluster-cluster aggregation simulation method. In the model, 3000 bi- and tri-functional monomers are first placed randomly in two halves of a three dimensional simulation box. The simulation proceeds by random displacement of each monomer and polymerization between adjacent monomers of different types, according to their remaining functional sites. Kinetic parameters of the reaction and structure characteristics of the film were studied and compared to mathematical models found in the literature. Our model shows a decrease in film thickness with an increase of initial volume fraction of monomers in the box, as been described in some experimental results. The surface-to-volume ratio of the film was found to be 2.1, which points to a dense film. This ratio decreases with simulation time and generally decreases with increased initial volume fraction, to form a looser structure in lower density systems. The charge distribution, represented by the distribution of unreacted functional groups in the film shows a trend for separation between negative and positive charge. These results are in qualitative agreement with a mathematical model by Freger and Srebnik (2003). The kinetics parameters mostly showed a qualitative agreement with a mathematical model by Freger (2005). According to our model, the dense core of the film grows proportionally to square of time and the reaction zone thickness is reduced with simulation running time. In the present simulation, the film seems to reach the stage of incipient film formation as a result of the small scale of the system. We conclude from the results that the interfacial polymerization process could be simulated by computer and could be improved when upgrading the size of the simulation and taking into consideration more realistic parameters, such as reaction probability and diffusion of reaction byproduct. A continuation of this work could focus on studying the characteristics of the film that are important for membrane performance.