@article{SindersbergerPremMonkman, author = {Sindersberger, Dirk and Prem, Nina and Monkman, Gareth J.}, title = {Self-assembling structure formation in low-density magnetoactive polymers}, series = {Journal of Applied Polymer Science}, volume = {137}, journal = {Journal of Applied Polymer Science}, number = {3}, publisher = {Wiley}, doi = {10.1002/app.48291}, 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.}, language = {en} } @article{PremChavezVegaBoehmetal., author = {Prem, Nina and Chavez Vega, Jhohan Harvey and B{\"o}hm, Valter and Sindersberger, Dirk and Monkman, Gareth J. and Zimmermann, Klaus}, title = {Properties of Polydimethylsiloxane and Magnetoactive Polymers with Electroconductive Particles}, series = {Macromolecular Chemistry and Physics}, volume = {219}, journal = {Macromolecular Chemistry and Physics}, number = {18}, publisher = {Wiley}, doi = {10.1002/macp.201800222}, abstract = {Magnetoactive polymers are intelligent materials whose mechanical and electrical characteristics are reversibly influenced by external magnetic stimuli. They consist of a highly elastic polymer matrix in which magnetically soft and/or hard particles are distributed by means of special fabrication processes. In addition to ferromagnetic particles such as carbonyl iron powder, electrically conductive particles may also be embedded into the polymer matrix. After characterizing a range of compounds, this work focuses on a comparison of the electrical properties and the suitability of various materials for applications, with particular emphasis on integration into 3D and 6D printing processes. 6D printing is based on the selective positioning of particles in a 3D polymer matrix with a further three degrees of freedom for a graduated dispersion of the particles at certain points and in desired directions. The aim is therefore to ensure that the polymers containing electroconductive tracks have the best possible electrical properties, that is, low resistivity but are still capable of being printed. A comparison between the traditionally used compounds containing graphite and carbon black is made for the first time. This latter is found to be greatly superior both in terms of electrical conductivity and applicability to 3D printing and 6D printing.}, language = {en} }