Polar–nonpolar interconnected elastic networks with increased permittivity and high breakdown fields for dielectric elastomer transducers

Abstract

Elastic materials with increased permittivity (ε′) were obtained in a three-step process starting from a hydroxyl end-functionalized polydimethylsiloxane (PDMS) of a high molecular weight (M_w = 139 kDa), trimethylsilyl end-blocked silicones that carry hydrosilane, cyanopropyl and hexyl groups P_x (where x represents the mol% of cyanopropyl groups), and tetraethoxysilane (TEOS). The hydrosilane groups of P_x were first hydrolyzed and the formed hydroxyl groups were subsequently reacted with partially hydrolyzed TEOS and further used as high ε′ components, cross-linkers, and reinforcing agents for the PDMS matrix. A high wt% of the polar component P_x was incorporated into the nonpolar PDMS matrix by forming interconnected networks. Thermal (DSC, DMA) and morphological investigations (SEM) show the biphasic morphology of the networks. The dielectric, mechanical, and electromechanical properties of the films were investigated. Materials with good elastic properties, increased ε′, and a high breakdown field (E_b) were obtained. The best material has an elastic modulus of 800 kPa at 10% strain, an ε′ = 4.5, and a maximum actuation strain of 8% at E_b = 56 V μm⁻¹.