Journal of Membrane Science
Membrane preparation by sequential spray deposition of polymer PISA nanoparticles


In recent years, amphiphilic block copolymers have attracted great interest for their ability to self-assemble, which allows them to form various bottom-up nanostructured materials. Here we report the fabrication of a nano-structured membrane from sequential spray deposition of cationic and anionic di-block copolymer nanoparticles. Reversible Addition Fragmentation Chain Transfer (RAFT) aqueous emulsion polymerisation method was used to synthesis the cationic and anionic diblock copolymer nanoparticles via polymerisation induced selfassembly (PISA). The thin film membrane was then prepared by sequential deposition of these oppositely charged nanoparticles using spray coating. The prepared nanoparticles and the resulting membranes were fully characterised using microscopy methods (TEM, SEM and AFM), dynamic light scattering (DLS) and filtration tests using pure water and salt solution

Membrane preparation using spray coating

The prepared 20% w/w solutions containing the block copolymer nanoparticles were diluted down to 4% w/w using a mixture of deionized water and ethanol (37.5%: 62.5%). The diluted solutions were then transferred to a syringe and connected to the spray coater (Nadetech Innovations Company) equipped with a pump. Spraying was controlled using software (ND-SP Spray Coater).

Sample and displacement were set as follows: length starting point: 0 mm, width starting point: 0 mm, nozzle distance: 30 mm, sample length: 35 mm, and sample width: 35 mm. Spray process was set as: number of layers: 1, number of steps per layer: 5, wait time between layers: 0 or 30 s, syringe diameter: 22.1 mm, flow rate: 100 mL/h, and speed: 1000 mm/min. Combine pattern was used when spray coating. The block copolymer solutions were spray-coated onto a commercial Nylon membrane (Filtre Fiorini, average pore size of 0.2 µm). To prepare the thin film membrane, two syringes were loaded and the positively charged (cationic) and negatively charged (anionic) nanoparticles solutions (at 4% w/w) were alternatively deposited onto the substrate. Once the desired number of “layers” was reached, the membranes were stored in water to avoid drying and cracking.

Keywords: Sequential deposition; Spray coating; Amphiphilic block copolymer nanoparticles; Nano‐structured membranes; Polymerization induced self-assembly