Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion

Abstract

Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.

Charge tunable thin-film composite membranes by gamma-ray triggered surface polymerization

“…The performance of the materials were however, strongly reduced, which was attributed to the collapse of the supporting layer pores upon evaporation of solvent during the low pressure plasma operation. The membranes, exposed to the monomer molecules or simply to the reactant gas environment, were found to be progressively etched with increasing plasma density leading to lower separation performance 7, 13, 18 . Therefore, the route proposed with gamma-ray irradiation, operated at 1 atm and in mild conditions, offers a clear advantage compared to these previous works.…”

“…Analysis was performed with OPUS 7.2 software from the Bruker Corporation. Streaming potential tests were performed to measure the surface charge of the membranes after grafting with a Surpass Anton Paar Electro Kinetic Analyser (EKA) utilizing Visiolab software (version 2.2) following a previously described procedure 13 . The membranes were cut and taped onto a 20 mm × 10 mm adjustable gap cell.…”

Antibacterial Polymeric Films Fabricated by [2+2] Cycloaddition–Retroelectrocyclization and Ag+ Ion Coordination

“…Among the several different proposed mechanisms of the antibacterial activities, Ag + ions usually inactivate enzymes and proteins by interacting with their thiol groups. Polymeric materials containing Ag + ions or Ag nanoparticles (films, membranes, fibers, and gels) and their coatings on various materials have been the target of these types of studies . However, difficulties in homogeneously dispersing Ag + salts into polymeric materials remained due to the poor miscibility of inorganic salts within organic polymers.…”

“…Polymeric materials containing Ag + ions or Ag nanoparticles (films, membranes, fibers, and gels) and their coatings on various materials have been the target of these types of studies. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] However, difficulties in homogeneously dispersing Ag + salts into polymeric materials remained due to the poor miscibility of inorganic salts within organic polymers. The Ag + salts partially release Ag + ions at certain stages, but the poor diffusibility of the Ag + ions over hydrophobic non-polar polymers often reduces the antibacterial activities.…”

Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

“…Plasma activation routes are versatile and environmentally friendly techniques which only utilize gas as a reactant to rapidly and uniformly modify surfaces 11 . Such techniques have been successfully used for almost four decades to treat bulk polymers and have been applied across a range of industries, including microelectronics, biomedicine, packaging and, more recently, membrane science 12 13 14 15 . Plasma glows are complex environments, where ionized species, elementary particles and ultra-violet (UV) radiation are simultaneously generated and co-exist and are able to initiate and promote reconfiguration of chemical bonds as well as inducing bond scission 16 .…”