Colloidal Polymers of Iron Oxide Cubes Prepared by Dipolar-Driven Assembly and in Situ Welding with Silica

The assembly of colloids under directional interactions is a powerful way to create 1D chain-like structures (colloidal polymers). However, these colloidal polymers usually disassociate into separate colloids when the surrounding conditions are changed, and additional solidification treatments are required. Herein, we report an in situ welding of colloidal polymers simultaneous with assembly process in solution. When dispersed in a solution containing trace amounts of water, iron oxide dipolar cubes self-associate into chains, and the simultaneous in situ hydrolysis-condensation of tetraethylorthosilicate welds these chains into permanent colloidal polymers. With low water contents, the 1D colloidal assembly is directed by self-induced dipolar interactions via the step-growth mechanism, and the water content has no significant effect on the assembly process but changes the silica shell thickness on the colloidal polymers. With higher water contents, 2D and 3D structures are formed due to the nondirectional attraction of the water on the colloids.