The success of dielectric elastomer materials in actuator technology as well as in energy harvesting is much influenced
by the material parameters, e.g. breakdown field, dielectric constant, and elastic modulus which have a direct impact on
the driving voltage. By increasing the dielectric constant of a material the activation voltage can be decreased, however
this increase is very often associated with a decrease in the breakdown field. In this proceeding, dielectric elastomer
materials based on polydimethylsiloxanes with increased strain at break and high breakdown fields are presented.
Dielectric elastomer actuators (DEAs) have attracted increasing attention over the last few years owing to their
outstanding properties, e.g. their large actuation strains, high energy density, and pliability, which have opened up a wide
spectrum of potential applications in fields ranging from microengineering to medical prosthetics. There is consequently
a huge demand for new elastomer materials with improved properties to enhance the performance of DEAs and to
overcome the limitations associated with currently available materials, such as the need for high activation voltages and
the poor long-term stability. The electrostatic pressure that activates dielectric elastomers can be increased by higher
permittivity of the elastomer and thus may lead to lower activation voltages. This has led us to consider composite
elastomeric dielectrics based on thermoplastic elastomers or PDMS, and conductive polyaniline or ceramic (soft doped
PZT) powder fillers. The potential of such materials and strategies to counter the adverse effects of increased
conductivity and elastic modulus are discussed.
In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve
control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace
conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar
properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric
elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices.
The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the
problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending
them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and
modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler
material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and
electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already
observed for blends of an olefin based thermoplastic elastomer and PANI.
The dielectric constant (ε) of a polymer can significantly be increased by blending it with conducting fillers. Given our
interest in developing highly efficient and long-lasting actuators for muscle replacement, we set out to explore all key
issues which could help to reduce the required voltage and at the same time ensure long term stability. The presentation
describes experiments which prove that the water content in carboxylic acid-decorated phthalocyanines (Pcs), commonly
falsely referred to oligo-Pcs, is a critical factor determining the absolute value of ε. Several publications on ε values of these oligo-Pcs led to contradicting conclusions because the effect of water was not sufficiently considered. The water
content is relevant because o-Pcs are often used as fillers to increase ε of polymer matrices. This presentation also
describes an experimental evaluation on whether or not as-prepared polyaniline (PANI) and poly(divinyl benzene)-
encapsulated (PDVB) PANI can be reasonably used as high ε fillers in matrix materials. For this purpose several blends
with polystyrene-polybutadiene block copolymer gels (PS-<i>b</i>-PB) and polydimethyl siloxane (PDMS) were prepared and
their dielectric properties investigated. The former part of this presentation has in part already been published (D. M.
Opris et al. Chem. Mater. 20(21), 6889-6896, 2008), the latter is completely new.