3 research outputs found
Nanostructured Block-Random Copolymers with Tunable Magnetic Properties
It was recently shown that block copolymers (BCPs) produced
room-temperature
ferromagnetic materials (RTFMs) due to their nanoscopic ordering and
the cylindrical phase yielded the highest coercivity. Here, a series
of metal-containing block-random copolymers composed of an alkyl-functionalized
homo block (C<sub>16</sub>) and a random block of cobalt complex-
(Co) and ferrocene-functionalized (Fe) units was synthesized via ring-opening
metathesis polymerization. Taking advantage of the block-random architecture,
the influence of dipolar interactions on the magnetic properties of
these nanostructured BCP materials was studied by varying the molar
ratio of the Co units to the Fe units, while maintaining the cylindrical
phase-separated morphology. DC magnetic measurements, including magnetization
versus field, zero-field-cooled, and field-cooled, as well as AC susceptibility
measurements showed that the magnetic properties of the nanostructured
BCP materials could be easily tuned by diluting the cobalt density
with Fe units in the cylindrical domains. Decreasing the cobalt density
weakened the dipolar interactions of the cobalt nanoparticles, leading
to the transition from a room temperature ferromagnetic (RTF) to a
superparamagnetic material. These results confirmed that dipolar interactions
of the cobalt nanoparticles within the phase-separated domains were
responsible for the RTF properties of the nanostructured BCP materials