Electroactive and electrostructured elastomers

Electroactive elastomers are composites made of solid particles embedded in an elastomeric network whose mechanical or optical properties can be chang ed by the application of an electric or a magnetic field. These materials h ave obviously a strong connection with ER and MR fluids and on be more appr opriated for some applications. We present recent results concerning two ki nds of filled elastomer, one based on carbonyl iron particles and the secon d one on silica particles. In the first case we show that the change of ela stic properties obtained by the application of a magnetic field depend dram atically on the way we have structured the suspension before the polymeriza tion. We explain quantitatively these experimental results with the help of finite element calculation to predict the magnetic forces between the part icles. In the second case we show how it is possible to modulate the transm ission of a laser beam by shearing a thin elastomeric film whose particles have been initially aligned with the help of an electric field. Some applic ations related to the organization of the filler particles by the applicati on of a field or a combination of a field and a flow before polymerization will be discussed.