Influence of the particle size on the properties of polyacrylamide ferrogels with embedded micron-sized and nano-sized metallic iron particles

摘要

Micron-sized zero-valent iron magnetic particles (MMPs) and iron magnetic nanoparticles (MNPs) were used for the synthesis of polyacrylamide (PAAm) ferrogels by radical polymerization in water solution. The interfacial adhesion of PAAm subchains of the gel network to the surface of MMPs and MNPs was determined in model composites, which comprised linear PAAm and magnetic particles. The enthalpy of interaction was evaluated by isothermal calorimetry using thermochemical cycle. MMPs and MNPs differed in the enthalpy of interaction with PAAm. It was positive in the former case and negative in the latter case. It meant that MNPs interacted with PAAm much stronger than MMPs. The enhanced interaction of MNPs with subchains of ferrogel network resulted in lower swelling and higher mechanical strength. Meanwhile the deformation of both types of ferrogels in 420 mT uniform magnetic field was found less sensitive to the interfacial adhesion and to the characteristic dimensions of the embedded iron particles.