Magnetic cluster-encapsulated polymer dimers with controlled surface property

This work reports the fabrication of magnetic polymer dimers with controlled surface anisotropy. The fabrication process involves the preparation of magnetite (Fe₃O₄) magnetic clusters with strong magnetism, followed by their surface modification, dispersion polymerization while using them as seeds, multilayer shell formation via layer-by-layer deposition, and polymer core swelling. The interplay between the swelling and multilayer shells generates pressure inside the multilayer-deposited, magnetic polystyrene (PS) spheres, forming structurally anisotropic dimers with single PS protrusions anchored on the multilayer surfaces within minutes. The use of titania precursor and different swelling agents, along with the change in the composition of the multilayer shell, enables the introduction of different surface anisotropies, such as the surface-charge anisotropy, anisotropic hydrophilicity/hydrophobicity, and material composition anisotropy, to the dimers. The strong magnetic response of the dimers, attributed to the magnetic cluster seeds, in combination with the surface-charge and material composition anisotropies allows a rapid magnetic recovery and an excellent reusability, enabling their application to 20-cycled reduction of 4-nitrophenol (4-NP) and methylene blue (MB) without loss of catalytic activity. Furthermore, the anisotropic hydrophilicity/hydrophobicity makes the dimers potentially useful as solid surfactant to stabilize immiscible oil–water mixture.