The improvement of the mechanical properties of polymer films by inclusion of mineral particles is a well known industrial practice used since the end of the XIX century. A classical example is the rubber industry for which the addition of carbon black as fillers permits to increase the elastic modulus of the pneumatics. Nevertheless, the mechanisms which govern the reinforcement properties are still not completely described by experiments and theory.

More recently, the use of fillers of nanometric size and of controlled geometry like colloidal silica allowed significant advances in the understanding of these mechanisms and in the conception of innovative materials. In this context, an original approach is to try to improve and to control the specific properties of the material with an external trigger like a magnetic field. We have obtained polymer films with anisotropic mechanical properties by inclusion of magnetic particles inside the matrix which can be aggregated in a controlled way during the film processing and oriented with an external magnetic field. The orientation of the fillers during the processing condition with the field is a new approach when magnetic composites are usually exploited to modulate the mechanical properties after the synthesis. More...