Molchanov Vyacheslav S, Pletneva Vera A, Klepikov Ilya A, Razumovskaya Irina V, Philippova Olga E
Physics Department, Moscow State University 119991 Moscow Russia
Moscow State University of Education 119991 Moscow Russia.
RSC Adv. 2018 Mar 23;8(21):11589-11597. doi: 10.1039/c8ra01014e. eCollection 2018 Mar 21.
The paper describes a new type of soft magnetic nanocomposite (SMN) based on a transient network of wormlike surfactant micelles with embedded oppositely charged submicron particles of magnetite acting as cross-linking agents. We study the change of the rheological properties of the SMNs with different contents of particles in response to magnetic field. We show that even at low field strengths the system acquires solid-like behavior, which can be attributed to the aggregation of particles into chain-like/column structures. A solid-like behavior appears at a rather small volume fraction of particles (0.002-0.04) indicating weak restrictions imposed by the matrix to the reorganization of particles under magnetic field, which can be due to the self-assembled structure of the micellar network. In the oscillatory rheological measurements, SMNs show a linear viscoelastic response in an unusually wide region of values of strain, magnetic field strength and content of particles, which is caused by the viscoelastic contribution of the micellar network. Upon gradual increase of magnetic field strength , the dynamic moduli ' and '' demonstrate slow growth followed by a sharp rise with a scaling law and reach a plateau at 0.15 T. The highest values of the storage modulus ' in SMNs are close to those in magnetorheological fluids with liquid Newtonian carrier, where particles move freely and the ' value is defined by the interactions of magnetized particles and chain-like/columns structures. SMNs have a yield stress, which grows with the increase of magnetic field strength and finally levels off just at the same magnetic field strength at which the ' and '' values reach a plateau indicating the saturation of the particles magnetization. The concentration dependencies of the elastic modulus and yield stress suggest the transition from chain-like to columnar structures of the particles. The new SMNs possessing the features of both magnetic fluids and magnetic gels have promising potential in a wide range of applications requiring responsiveness to magnetic field.
本文描述了一种新型软磁纳米复合材料（SMN），它基于蠕虫状表面活性剂胶束的瞬态网络，其中嵌入了带相反电荷的亚微米级磁铁矿颗粒作为交联剂。我们研究了不同颗粒含量的SMN在磁场作用下流变性质的变化。我们表明，即使在低场强下，该系统也会呈现出类固体行为，这可归因于颗粒聚集成链状/柱状结构。在相当小的颗粒体积分数（0.002 - 0.04）下就出现了类固体行为，这表明基体对磁场作用下颗粒重组的限制较弱，这可能是由于胶束网络的自组装结构所致。在振荡流变测量中，SMN在应变、磁场强度和颗粒含量的异常宽的值域内表现出线性粘弹性响应，这是由胶束网络的粘弹性贡献引起的。随着磁场强度逐渐增加，动态模量G'和G''呈现出缓慢增长，随后以标度律急剧上升，并在0.15 T时达到平台期。SMN中储能模量G'的最高值接近具有液体牛顿载体的磁流变液中的值，在磁流变液中颗粒可自由移动，G'值由磁化颗粒与链状/柱状结构的相互作用决定。SMN具有屈服应力，其随磁场强度的增加而增大，最终在G'和G''值达到平台期的相同磁场强度处趋于平稳，这表明颗粒磁化达到饱和。弹性模量和屈服应力的浓度依赖性表明颗粒从链状结构转变为柱状结构。这种兼具磁性流体和磁性凝胶特征的新型SMN在需要对磁场有响应的广泛应用中具有广阔的前景。
