Simulation of the Response of Microferrogel to External Magnetic Field

Abstract

A coarse-grained molecular dynamics method is used to investigate a. microferrogel (MFG); a. small polymer object containing nanoparticles of magnetoactive filler. Despite the fact that an applied magnetic field acts directly on only the nanoparticles, structural and mechanical changes occur throughout the entire composite system due to the coupling between these particles and the polymer. The study of these changes is important in view of widely discussed prospects of using MFGs as field-controlled microcontainers for delivering bioactive substances or drugs. In this work, a. numerical model is proposed and realized, which enables one to perform a. detailed analysis of stationary states of an MFG suspended in a. neutral solvent. The effect of concentration of particles and their magnetic characteristics (magnetic moment magnitude, degree of uniaxial magnetic anisotropy, and interparticle dipolar coupling parameter) on the structure formation in the absence of an external magnetic field and under its influence is investigated. It is shown that the chain-like clusters are in fact the only type of aggregates arising in MFG. However, their effect on the polymer subsystem depends strongly on the type of magnetic anisotropy and on the magnetic phase concentration. This, in turn, entails different scenarios of the mechanical response of MFG and, in particular, differently affects the change in the amount of solvent present in the sample.