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Effects of Polyamide Chemistry on Solution Permeance in Molecular Layer-By-Layer Desalination Membranes



William Mulhearn, Christopher Stafford


We present a series of polyamide membranes synthesized via molecular layer-by-layer (mLbL) deposition, using a combination of two acid chlorides: trimesoyl chloride (TMC) and isophthaloyl chloride (IPC), and one of two diamines: m¬-phenylenediamine (MPD) or 3,5-diaminobenzoic acid (BA). These monomer combinations permit comparison of the conventional reverse osmosis chemistry, TMC combined with MPD, against a variant with a higher concentration of polar acid groups but similar cross-link density, TMC combined with BA, and a variant with reduced cross-link density but similar concentration of polar acid groups, a 50% / 50% mixture by mass of TMC and IPC combined with MPD. Water permeance, NaCl rejection, and water swelling are compared across the series, and the results are interpreted according to the solution-diffusion (SD) and pore flow (PF) models of solution transport. We find that the rate of water transport is most strongly controlled by the concentration of hydrophilic moieties in the membrane, and that the PF model provides a more physically consistent description of this polyamide system than the SD model.
ACS Applied Polymer Materials


polyamide, membranes, desalination, molecular layer-by-layer deposition, solution-diffusion, pore flow


Mulhearn, W. and Stafford, C. (2022), Effects of Polyamide Chemistry on Solution Permeance in Molecular Layer-By-Layer Desalination Membranes, ACS Applied Polymer Materials, [online],, (Accessed April 19, 2024)
Created April 1, 2022, Updated January 27, 2023