Tunable magneto-responsive mesoporous block copolymer membranes

Abstract Mesoporous magneto-responsive membranes with remote-controllable step-wise tunable changes of sieving barrier pore size were successfully prepared. The membranes were composed of a thin mesoporous size-selective layer containing iron oxide nanoparticles (IONPs) embedded in poly(oligo(ethylene glycol) methyl ether methacrylate)- block -polystyrene- block -poly(oligo(ethylene glycol) methyl ether methacrylate) (PMEO n MA- b -PS- b -PMEO n MA), on top of a polyvinylidene fluoride (PVDF) macroporous support membrane. IONPs and PMEO n MA- b -PS- b -PMEO n MA mixture solutions were spun-cast on PVDF membranes, and then mesopores were introduced into the hydrophilic PMEO n MA domains by controlled selective swelling with a mixture of methanol and supercritical CO 2 . The loaded IONPs aggregated into small clusters (0.1–1 µm) and were finely dispersed in the PMEO n MA- b -PS- b -PMEO n MA mesoporous top layer. No defect was found in the membranes with IONPs based on water and dextran ultrafiltration performances, and scanning electron microscopy (SEM) images showed that their barrier pore sizes were almost identical to those of no IONPs containing membranes. Upon stimulation with alternating magnetic field with different input energy, the water permeability as well as the dextran rejection were tuned into different levels, indicating that the sieving barrier pore size distribution of these thin-film mixed matrix nanocomposite membranes was step-wise adjustable.