A novel method allowing rapid production of reliable composites with increased dielectric constant and high dielectric strength for dielectric elastomer actuators (DEA) is reported. The promising approach using composites of conductive particles and insulating polymers generally suffers from low breakdown fields when applied to DEA devices. The present publication shows how to overcome this deficiency by using conductive polyaniline (PANI) particles encapsulated into an insulating polymer shell prior to dispersion. PANI particles are encapsulated using miniemulsion polymerization (MP) of divinylbenzene (DVB). The encapsulation process is scaled up to approximately 20 g particles per batch. The resulting particles are used as high dielectric constant (ϵ′) fillers. Composites in a polydimethylsiloxane (PDMS) matrix are prepared and the resulting films characterized by dielectric spectroscopy and tensile tests, and evaluated in electromechanical actuators. The composite films show a more than threefold increase in ϵ′, breakdown field strengths above 50 V μm−1, and increased strain at break. These novel materials allow tuning the actuation strain or stress output and have potential as materials for energy harvesting.

Several polydimethylsiloxane elastomers were developed and investigated regarding their potential use as materials in dielectric elastomer actuators (DEA). A hydroxyl end‐functionalized polydimethylsiloxane was reacted with different crosslinkers and the electromechanical properties of the resulting elastomers were investigated. The silicone showing the best actuation at the lowest electric field was further used as matrix and compounded with encapsulated conductive polyaniline particles. These composites have enhanced properties including increased strain at break, higher dielectric constant as well as, gratifyingly, breakdown fields higher than that of the matrix. One of the newly synthesized composites is compared to the commercially available acrylic foil VHB 4905 (3M) which is currently the most commonly used elastomer for DEA applications. It was found that this material has little hysteresis and can be activated at lower voltages compared to VHB 4905. For example, when the newly synthesized composite was 30% prestrained, a lateral actuation strain of about 12% at 40 V μm−1 was measured while half of this actuation strain at the same voltage was measured for VHB 4905 film that was 300% prestrained. It also survived more than 100 000 cycles at voltages which are close to the breakdown field. Such materials might find applications wherever small forces but large strains at low voltages are required, in, for example, tactile displays.

The low frequency mechanical and dielectric behavior of three different elastomers has been investigated by dynamic mechanical analysis and dielectric spectroscopy, with the aim of accounting for the frequency dependence of the characteristics of the corresponding dielectric elastomer actuators. Satisfactory agreement was obtained between the dynamic response of the actuators and a simple model based on the experimental data for the elastomers, assuming that the relatively large prestrains employed in the actuators to have little influence on the frequency dependence of their effective moduli. It was thus demonstrated that the frequency dependence of the actuator strain is dominated by that of the mechanical response of the elastomer, and that the frequency dependence of the dielectric properties has a relatively minor influence on the actuator performance.

An improved synthesis of photosensitive homopolymers containing aryltriazene chromophores covalently incorporated into the polymer backbone is reported. Such photopolymers proved to have promising properties for novel UV‐laser applications. A homologous series of new aryltriazene polymers with increasingly branched side chains (R = Me, Et, iPr, tBu) was synthesized and characterized. Homogeneous thin films with thicknesses from ≈15 to >150 nm were prepared by spin‐coating. Photodecomposition was studied in solution and on thin films. Polymers with increasingly branched and bulky substituents showed decreasing photodissociation rates. NMR studies suggested an enhanced hindrance of the N(2)–N(3) bond rotation in the aryltriazene moiety with increasing steric demand of the substituents.

Monomeric phthalocyanine pentylester derivatives containing Cu and Zn were synthesized via the cyclotetramerization of 4,5-dipentylphthalonitrile. Conversion of the pentylester derivatives by hydrolysis yielded the octacarboxylic acid phthalocyanine derivatives in high purity, without any contamination by oligomers. The dielectric properties of pressed pellets were investigated as a function of frequency. When exposing the phthalocyanine powders to water vapor, a high increase in the dielectric constant was found for the carboxylic acid derivatives, whereas the esters showed no effect. For Cu containing octacarboxylic acid phthalocyanine derivatives, the low-frequency dielectric constant of the pellets was raised from 12 to >1 × 105 when going from a water content of 6.4 to 14.7 wt %, respectively. The concomitant sharp rise in conductivity was attributed to the protons released from the acid groups after water uptake. The present work clearly demonstrates that water uptake and not oxygen is the major factor for achieving surprisingly high dielectric constants in carboxylic acid phthalocyanine derivatives.

Cover: The figure shows a SEM picture of a smooth aryltriazene photopolymer film (thickness 360 nm): part of a typical ablation spot done by 6 pulses of an excimer laser (l = 308 nm, 90 mJ/cm 2 ), demonstrating the clear cut edges and the absence of debris or carbonization. An improved synthesis for such thin-film forming photopolymers was reported. Further details can be found in the Full Paper by M. Nagel,* R. Hany, T. Lippert, M. Molberg, F. A. Nüesch, and D. Rentsch on page 277.

The dielectric constant () 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. Several publications on 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 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 fillers in matrix materials. For this purpose several blends with polystyrene-polybutadiene block copolymer gels (PS-b-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.

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.