High-permittivity silicone dielectric elastomers compatible with ionic liquid-grafted chloropropyl-silicone oil

Abstract

Dielectric elastomers (DEs) can undergo very large spatial deformations in response to an externally applied electrical field, giving them significant potential as soft actuators. High-performance DEs are usually modified by high-permittivity additives, which are used to lower driving voltages. In this study, a novel high-permittivity soft additive (LMS-EIL) was developed via the combination of high-permittivity ionic liquid (IL) and chloropropyl-silicone, enabling good compatibility with the silicone matrix. The relative dielectric permittivity of the novel silicone oil additive was 9×10 4 times higher at 0.1Hz compared to pristine chloropropyl-silicone oil. High-permittivity silicone elastomers were then achieved via incorporation of this novel IL-grafted chloropropyl-silicone oil. The relative dielectric permittivity of elastomers modified with 10 parts per hundred rubber (phr) LMS-EIL increased from 3.0 (pure film) to 22 at 0.1Hz, while the Young's modulus decreased steadily with increasing LMS-EIL concentration. A simplified figure of merit (Fom') was used to evaluate actuation performance, and was shown to be 8.1 for the elastomer incorporated with 10 phr LMS-EIL, indicating excellent potential for use as an actuator.

High‐Permittivity Polysiloxanes for Solvent‐Free Fabrication of Dielectric Elastomer Actuators

“…Kang [28] 5.6 / 3.9 (1 MHz) a) Permittivity of 5.6 measured for elastomer with 15 phr ionic liquid showing phase separation, 3.9 measured for 10 phr ionic liquid showing no phase separation; b) Not detected, below the lower limit of the DSC temperature range www.advmattechnol.de and, thus, the degree of polymerization. [33,34] A sufficient molar mass of the vinyl-terminated polymer is necessary to achieve suitable mechanical properties, especially high strain at break.…”

“…The permittivity of 6.4 is still significantly higher than the permittivity reported in the literature for other chloro-functional polysiloxanes. [27][28][29] For polymer P 70 2, we also performed temperature-dependent impedance spectroscopy in the range of −100 °C to +50 °C in 10 °C steps (Figure 3b; Figure S9b, Supporting Information). At the T g , the movement of the polymer chain segments is enabled, which leads to a steep increase in permittivity.…”

“…The elastomer blend of PDMS and a chloro-functional ionic liquid developed by Kang et al reaches a large strain at break of 321% and a comparable breakdown field of 20 V µm −1 . [28] However, the elastomer showed a permittivity of only 3.9 and the elastic properties were not examined.…”

“…Therefore, a balance between the increased permittivity and low conductivity needs to be found. Polysiloxanes bearing chloro‐functional side groups for enhanced permittivity have previously been reported by the groups of Skov [ 27,28 ] and Racles. [ 29 ] Racles et al.…”

“…Kang et al prepared blends based on a PDMS matrix filled with an ionic liquid filler. [28] The ionic liquid was synthesized starting from a polysiloxane with 14-16% chloropropyl groups and substituting 30% of the chloropropyl groups with imidazole groups. The blend with an ionic liquid content of 15 phr reached a permittivity of 5.61 at 10 6 Hz, but aggregation of the ionic liquid is observed.…”