ИСТИНА

Magnetoactive elastomers (MAEs) are composite materials consisting of magnetic microparticles embedded into a polymer matrix. In magnetic field particles tend to restructure and form column-like or chain-like structures along the field lines. This leads to considerable changes in viscoelastic properties of the material under an applied magnetic field. Magnetic response of MAEs depends on the balance of magnetic forces acting between filler particles in magnetic fields and elastic forces of the polymer matrix, trying to return magnetic particles to their initial positions. Thus, soft enough matrices should be used in order to obtain a high magnetic response of MAEs. Usually a low-molecular-mass solvent is used as plasticizer to decrease the elastic modulus of matrices, but it meets a disadvantage: liquid tends to flow out from MAEs with time. To solve this problem and to keep elastomer soft we developed a matrix containing dangling chains, chemically connected to cross-links (fig.1). Elastomers based on PDMS were synthesized. Concentration of the hydride containing cross-linking agent was varied. It was shown that the cross-linking process is quick: 1 hour annealing is already enough to form a cross-linked matrix. Catalytic process could be slowed down by addition of pyridine to Pt-based catalyst so that the cross-linking process can be triggered at high temperatures (~100ºC). Rheological measurements showed that shear storage modulus of such elastomers can be varied from very low (~1kPa) to medium (~20kPa) values. MAEs based of these matrices containing various concentrations of carbonyl iron particles (from 70 to 80 mass%) were obtained. Relative growth of the shear modulus of synthesized MAEs in applied magnetic field of 1T is more than 2 orders of magnitude.