A novel method is established for permittivity enhancement of a silicone matrix for dielectric elastomer actuators (DEAs) by molecular level modifi cations of the elastomer matrix. A push-pull dipole is synthesized to be compatible with the silicone crosslinking chemistry, allowing for direct grafting to the crosslinker molecules in a one-step fi lm formation process. This method prevents agglomeration and yields elastomer fi lms that are homogeneous down to the molecular level. The dipole-to-silicone network grafting reaction is studied by FTIR. The chemical, thermal, mechanical and electrical properties of fi lms with dipole contents ranging from 0 wt% to 13.4 wt% were thoroughly characterized. The grafting of dipoles modifi es the relative permittivity and the stiffness, resulting in the actuation strain at a given electrical fi eld being improved by a factor of six.

Block copolymer elastomer conductors (BEC) are mixtures of block copolymers grafted with conducting polymers, which are found to support very large strains, while retaining a high level of conductivity. These novel materials may find use in stretchable electronics. The use of BEC is demonstrated in a capacitive strain sensor and in an artificial muscle of the dielectric elastomer actuator type, supporting more than 100% actuation strain and capacity strain sensitivity up to 300%.

Silicone elastomers are highly suitable for application in the field of dielectric elastomer actuators (DEA) due to their unique material properties (e.g. low glass temperature, thermal stability, large capability of chemical tailoring). The elastomer forming Polydimethysiloxane (PDMS) employed for this study consists of chains with vinyl termination and is cross linked via hydrosilylation to a cross linking molecule in the presence of platinum catalyst. Here, dipole molecules (N-Allyl-N-methyl-4-nitroaniline) were specifically synthesized such that they could chemically graft to the silicone network. The most prominent advantage of this approach is the achievement of a homogeneous distribution of dipoles in the PDMS matrix and a suppression of phase separation due to the grafting to the junction points of the rubber network. Several films with dipole contents v ranging from 0 % wt up to 10.9 % wt were prepared. The films were investigated to determine their mechanical (tensile testing), dielectric (dielectric relaxation spectroscopy) and electrical (electrical breakdown) properties. This new approach for composites on the molecular level leads to homogeneous films with enhanced material properties for DEA applications. An increase in permittivity from 3.3 to 6.0, a decrease in electrical breakdown from 130 V/μm to 50 V/μm and a lowering of the mechanical stiffness from 1700 kPa to 300 kPa was observed. © 2011 SPIE

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