Smart composites with controlled anisotropy

The new generation of magnetic elastomers represents a new type of composites, consisting of small (mainly nano- and micron-sized) magnetic particles dispersed in a high elastic polymeric matrix. The combination of polymers with magnetic materials displays novel and often enhanced properties. The magnetic particles couple the shape of the elastomer to the external magnetic field. All of the forces acting on the particles are transmitted directly to the polymer chains resulting in either locomotion or deformation. Shape distortion occurs instantaneously and disappears abruptly when external field is applied or removed, respectively. Combination of magnetic and elastic properties leads to a number of striking phenomena that are exhibited in response to impressed magnetic field. Giant deformational effect, tuneable elastic modulus, non-homogeneous deformation and quick response to magnetic field open new opportunities for using such materials for various applications. Elastic material.,; with tailor-made anisotropy can also be prepared under external field. The anisotropy manifests itself in both direction dependent elastic modulus as well as direction dependent swelling. (c) 2005 Elsevier Ltd. All rights reserved.