Magnetic Heat Generation Mechanisms of Iron Oxide–Poly(ethylene oxide) Nanocomposites*

Remote triggering of smart materials such as shape memory polymers and nanocomposites for drug delivery are research areas of continued interest. Magnetically susceptible nanoparticles (NPs) generate heat when exposed to an alternating magnetic field (AMF), making these NPs an ideal candidate for use in smart nanocomposites. Current work studies the dependence of heat generation mechanisms and interfacial heat transfer on the matrix molecular weight and NP concentration in iron oxide (Fe₃O₄)–poly(ethylene oxide), PEO, nanocomposites. Understanding the rotational dynamics of magnetic NPs is important in the application areas of these nanocomposites. The relative importance of Brownian and Neel relaxation processes is determined by altering the polymer matrix viscosity. Single core amine coated 10–nm–diameter Fe₃O₄ NPs were dispersed at concentrations less than 1% by weight in PEO matrices with varying molecular weights. Altering the matrix viscosity by varying the molecular weight of the PEO allows for consistent intermolecular interactions between the NPs surface groups and the PEO. The viscoelastic properties of these materials were also studied via nanoindentation.