Interfacial Polymerization of Aromatic Polyamide Reverse Osmosis Membranes.

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Polyamide membranes are crucial for reverse osmosis (RO) water treatment.
• The precise mechanism of interfacial polymerization during their formation remains incompletely understood.

Purpose of the Study:

• To elucidate the atomistic mechanism of interfacial polymerization between trimesoyl chloride (TMC) and m-phenylenediamine (MPD) monomers.
• To investigate the role of the aqueous-organic interface in controlling cross-linking kinetics and membrane structure.

Main Methods:

• Atomistic molecular dynamics simulations were employed to model the cross-linking process at the solution interface.
• Explicit solvent models were used to capture the interactions between monomers and solvents.

Main Results:

• The solution interface acts as a "concentration and dispersion" site for monomers, initiating rapid cross-linking.
• A precross-linked film forms, initially slowing kinetics, but interfacial fluctuations and solvent interactions promote further cross-linking.
• Monomer solubility in different organic solvents (cyclohexane vs. n-hexane) impacts cross-linking rate, surface homogeneity, and subnanopore characteristics.

Conclusions:

• The study provides critical insights into the interfacial polymerization mechanism governing polyamide membrane formation.
• Understanding these dynamics in explicit solvents is vital for designing advanced polyamide membranes with tailored properties for water treatment applications.