Ink-jet printing assisted fabrication of thin film composite membranes

• Ink-jet printing assisted fabrication (PAF) used for polyamide thin films.
• XPS showed extent of polyamide crosslinking and correlated to surface hydrophilicity.
• PAF allows controlled deposition of m-PDA, without draining or removal of droplets.
• PAF polyamide thin film morphology was similar to conventionally made membranes.

Modern printing techniques may facilitate membrane fabrication methods for the creation of novel polymer compositions and coatings. The interfacial polymerization reaction between diamine and triacyl chloride monomers is a highly efficient method to achieve currently used RO and NF thin film composite membranes. Here we present our investigation of the interfacial polymerization process using an ink jet printer for the application of an amine monomer to an ultrafiltration (UF) support as part of the polymerization method. In this study, single and multiple coatings of m-phenylene diamine (m-PDA) were applied to the UF support, without a draining step, before application of trimesoyl chloride (TMC). The resulting polymer films were characterized using FTIR and correlated to the amount of m-PDA printed on the UF support. The amount of crosslinking in the polyamide thin film increased as more m-PDA was printed on the support as indicated by XPS oxygen/nitrogen ratios. Also, the hydrophilicity of the surfaces could be explained with respect to the amount of polyamide crosslinking. SEM images of the membrane surfaces showed the progressive morphological changes to the surface as more m-PDA was printed. Salt rejection increased and the flux decreased as the amount of printed m-PDA increased, and was explained by amount of polymer crosslinking, surface hydrophobicity, and polyamide layer thickness. Further development of ink-jet printing within the context of interfacial polymerization methods, or for other membrane coating applications may accelerate the discovery of novel membranes, and lead to deeper understanding of membrane processes. Printing as a coating method exhibits higher accuracy and controllability compared to dip coating methods, that require removal of excess liquid or droplets via difficult to control draining or other steps, and which may eventually result in an overall more efficient fabrication process.

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