Magnetic Properties of Cobalt-Containing Diblock Copolymers with Cylindrical Morphology of Different Domain Sizes

Abstract

Previously, we have synthesized a cobalt-containing diblock copolymer system which exhibited room temperature ferromagnetic properties after phase separation and heat treatment. We have also shown that the morphology and cobalt density in the nanostructured domains both influenced the magnetic properties of these materials due to nanoconfinement which enhanced the dipolar interactions between otherwise superparamagnetic cobalt nanoparticles. Here, we investigated the effect of domain size on the magnetic properties of these room temperature ferromagnetic materials (RTFMs) using a series of five cobalt-containing diblock copolymers with various molecular weights and constant block ratios. The diblock copolymers self-assembled into cylindrical morphologies with different domain sizes upon solvent annealing, and then were converted to RTFMs upon a simple heat treatment. The domain sizes of these RTFMs did not show a significant impact on their coercivity values, possibly because the domain size range investigated was not large enough and the cobalt–cobalt dipolar interactions were nearly constant throughout. At the same time, this study confirms that the RTFMs generated from these novel block copolymers are robust.