Grönewald, Matthias (2013)
Ionenkomposite und Ionensiloxancopolymere und ihre Eignung als DEA.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

Ionenes are a group of macromolecules, the mainchain of which consists of ions or ionic groups. Due to their dielectric and electric properties its members are more and more in the focus of research groups. Dielectric elastomeric actuators (DEA), a group of electroactive polymers, are a possible application, which are increasingly relevant as actuators, sensors or for energy harvesting. Their electromechanical working principle is based on the electric field dependent attractive forces between overlapping compliant electrodes and the resulting deformation, respectively the change in capacity due to mechanical stress. In this work ionene composites based on PDMS and aliphatic ionenes and ionene copolymers and their suitability as new materials in actuator layers for DEA are investigated. For this different ionenes are synthetized and composites are produced as thin actuator membranes, which are then characterized concerning their morphology, dielectric, electric, mechanical and eventually electromechanical properties. By means of these investigations on composites it is shown that the approach of increasing the overall permittivity through ionenes as non-ohmic, conductive fillers leads to an increase of the relative permittivity. Associated with this is however a degradation in concern to the actuator performance of the mechanical properties in form of an increasing tensile modulus (YOUNG’s modulus), which is proportional to the filler content. Due to the usage of fillers additional material parameters are negatively influenced to the point that no considerably improved electromechanical system response could be achieved. As a result of the hydroscopic nature of the applied ionene fillers the surrounding humidity is an important parameter and its influence on the properties is particularly investigated with frequency dependent electric measurements. In this context a proof of concept for humidity sensors based on thin films of Poly-6,5 ammonium iodide is given. At last a novel ionene grafted siloxane copolymer is for the first time evaluated regarding its possible applicability in DEA and based on mechanical and dielectric data the electromechanical performance estimated. In context of the concept of DEA it is eventually shown, that opposing to composites with hard fillers, ionene siloxane copolymers provide a much more positive perspective for further investigations and therefore give the oppertunity to an emerging class of new electroactive polymers.

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