Silicone films by crosslinking of polymethylhydrosiloxanes with N,N-diallyl-4-nitroaniline

Dielectric elastomer actuators (DEAs) enable a wide range of interesting applications since they are soft, lightweight, low-cost and have direct voltage control. However, one of the main obstacles to their wide-spread implementation is their high operating voltage, which tends to be several thousand volts. The operating voltage can be lowered by reducing the thickness, increasing the permittivity or lowering the stiffness of the elastomer. Recently, we offered a method to increase the permittivity of silicones from 3 to 6 via dipole-grafting simultaneously accompanied by significant stiffness reduction. During network formation the used dipole N-allyl-N-methyl-4-nitroaniline and divinyl-terminated polydimethylsiloxane compete to bind covalently to the polymethylhydrosiloxane crosslinker. Therefore, the dipole is connected only as a side-group to the crosslinker. Here we present a new approach using the difunctional dipole N,N-diallyl-4-nitroaniline as crosslinker for polymethylhydrosiloxanes. The Pt-catalyzed crosslinking reaction is optimized to obtain qualified silicone films with different dipole concentrations varying from 0.5 wt% to 1 wt%. The mechanical properties, the permittivity and the electromechanical properties of the films were characterized for varying nitroaniline content. For these novel elastomer materials an actuation strain of 13 % was measured at 40 V/micrometers.