Self‐assembling structure formation in low‐density magnetoactive polymers

Abstract

The formation of microstructures in magnetoactive polymers (MAPs) is a recently discovered phenomenon found only with very low filler particle concentrations (less than 3 wt %). Due to the degassing process, filler particles collect around an ascending bubble, which dissolves at a certain point leaving particulate rings within the matrix. The formation of toroidal microstructures commences as filler concentration approaches 1 wt %. The development of coherent parallel aligned rings with a compact order continues as particle concentrations increase toward 2 wt %. Between 2 and 3 wt % capillary doublets develop, while mass percentages higher than 3% result in increasing entropy as the random order of particle agglomeration found in higher concentration MAP dominates. Self-structured samples of different filler material and concentrations between 1 and 3 wt % have been investigated using X-ray tomography, where the emerging structures can be observed and visualized. The ring structures resulting from this research represent microinductivities which can be fabricated in a targeted manner, thus enabling new applications in the high-frequency radio field. Furthermore, these anisotropic, but well-organized, structures have magnetic field-dependent implications for optical, thermal, acoustic, and medical applications.

Infrared spectral analysis of low concentration magnetoactive polymers

“…At higher CIP concentrations such ring formations tend to diminish and a more random anisotropic condition prevails. 17 The 2 wt% CIP MAP samples are the only ones, which show appreciable change at any IR wavelength and particularly at 4.255 μm (wavenumber 2350 cm −1 ). For these samples alone, an extremely clear structure becomes visible under X-ray computer tomography as can be seen in Figure 13.…”

“…During decavitation, the shedding of iron particles results in the formation of ring structures as the cavities ascend and eventually dissipate. 17 Should the concentration be high enough to ensure contiguation of rings then capillary doublets occur.…”

“…At higher CIP concentrations, the CIP density exceeds the level at which such structures can form resulting in an almost amorphous topology as found in MAP with higher CIP concentration. 17…”

Electrical properties of magnetorheological fluids

“…The relative permeabilities of MRFs lie typically between 3 and 7 for magnetizable content in the range 10 wt% to 30 wt% [Simon et al, 2001]. SQUID measurements in magnetoactive polymers reveal similar values and reveal that both the magnetic moment and the relative permeability does not increase linearly with magnetic content but often reaches a peak (typically at around 27 wt% CIP) with increasing CIP concentrations [Sindersberger et al, 2019]. FF have much lower permeability, around 1.2 [Mayer & Polcar, 2012].…”