Block copolymer based novel magnetic mixed matrix membranes-magnetic modulation of water permeation by irreversible structural changes

Abstract

This contribution focuses on understanding the effect of magnetic field intensity on the performance of novel hydrophilic and hydrophobic mixed matrix membranes (MMMs). The hydrophilic MMMs were made up of polymeric nanoparticles (PNPs) that were synthesized through polymerization-induced selfassembly (PISA) and iron oxide nanoparticles prepared in presence of poly (methacrylic acid)-bpolyquaternized (2-dimethylamino)ethyl methacrylate. The hydrophobic MMMs were prepared by the addition of iron oxide nanoparticles with different surface properties to a linear poly (methacrylic acid)-bpoly (methylmethacrylate) diblock copolymer dissolved in tetrahydrofuran (THF). Three different types of hydrophilic membranes were prepared with polymeric nanoparticles of different morphologies (spherical, vermicular and vesicular). In case of the hydrophobic membranes, six different membranes containing different iron oxide core coated with different stabilizers such as poly (methacrylic acid), quaternized poly(2-dimethylamino)ethyl methacrylate and meso-2,3-dimercaptosuccinic acid were prepared. An external magnetic field with intensity values up to 1.15 T was used for the permeation studies and the results were compared with those obtained in the absence of magnetic field. The collected data indicate an increase in the water flux of up to 16% and 29% under the magnetic field for hydrophobic and hydrophilic membranes, respectively. The STEM analyses suggest that the magnetic nanoparticles move within the membrane structure during the application of the magnetic field. This displacement/rearrangement causes constant changes in the membrane structure (structure of the active layer) and consequently on the membrane permeability. These results suggest that the application of the magnetic field could be used as a pretreatment step to obtain high flux membranes.

Influence of Magnetic Nanoparticles on PISA Preparation of Poly(Methacrylic Acid)‐b‐Poly(Methylmethacrylate) Nano‐Objects

“…These results are in accordance with our previously published work where STEM analyses of the membrane before, after, and during the membrane exposure to the magnetic field indicates a structural rearrangement of the nanoparticles induced by the application of the magnetic field. This structural rearrangement increases the void spaces hence the increase in the membrane hydraulic permeability . Given the similitude of the magnetic behavior of the membranes developed in the previous and present work, it is plausible to assume that the magnetically induced changes of permeate fluxes is also a consequence of reversible structural rearrangements of the membrane magnetic top layer.…”

“…Hybrid nanoparticles are extensively studied for drug delivery, cancer treatment, magnetic resonance imaging, antibacterial applications as well as in membrane science . The major problems associated with INPs are aggregation, colloidal stability, and long‐term stability . Encapsulation using amphiphilic block copolymers or decoration with water‐soluble polymers (bearing carboxylic acid and phosphoric acid side chains for example) are valuable strategies to solve these problems …”

“…Through electrostatic interaction, the positively charged INPs were attracted to the negatively charged polymeric nanoparticles (PNPs). Magneto‐responsive membranes were prepared using this solution containing a mixture of INPs and PNPs, forming nanoparticle layer at the surface of a nylon porous support . In this work, we look into the possibility of decorating PNPs with INPs using a one‐pot method.…”

“…The resulting iron‐oxide decorated nanoparticles had hydrodynamic diameter of 50 nm in ethanol. The behavior of the porous film under magnetic field was tested using a custom‐made cross‐flow cell. Figure shows the membrane performance under a magnetic field of 0.05 T. The water flux values were measured in cycles in the presence and absence of magnetic field.…”

Polymerizations by RAFT: Developments of the Technique and Its Application in the Synthesis of Tailored (Co)polymers

“…The (ir)reversibility depends to a large extent on the strength of the magnetic field and the time of exposure. [ 250,251 ] In a later work it was demonstrated that the pore size of such membrane could easily be tuned by varying the surface charge, size and the nature of the core–shell nanoparticles (both organic and inorganic). [ 252 ] In a different approach, instead of mixing the polymer nanoparticles with the inorganic iron‐oxide nanoparticles, the PMAA‐ b ‐PMMA particles were decorated with iron‐oxide cores through ligand exchange during nanoparticle synthesis.…”