Soft silicone elastomers exhibiting large actuation strains

Abstract

Poly(dimethyl-co-methylvinyl)siloxane-α,ω-diols with 1.5, 5.5, and 8.5 mol% vinyl group contents, respectively, are obtained via an environmental friendly synthesis and used as platforms for further chemical modification via a green process. This chemical modification consists of UV-activated thiol-ene addition of 3-chloro-1-propanethiol to the vinyl groups, as proven by NMR analysis.Cross-linking with tetraethyl orthosilicate (in excess) of such modified polymers leads to dielectric elastomers with higher values of dielectric permittivity than those of non-chemically modified vinyl copolymers cross-linked under similar conditions. In addition, at high chloropropyl content, there is a significant decrease in Young's modulus, attributed to the plasticizing effect of the alkyl segment of the attached chloropropyl, and only a slight increase in breakdown strength is observed. All these changes induced by the chloropropyl group act synergistically in favor of the electromechanical performances of the resulting elastomers that exhibit large out-of-plane actuation strains of 53% and 61% for polar contents of 5.5 and 8.5 mol%, respectively, at an applied electric field of 40 V/μm. These are to the best of our knowledge the largest out-ofplane actuation strains from silicone elastomers reported in literature.

Crosslinking Methodology for Imidazole-Grafted Silicone Elastomers Allowing for Dielectric Elastomers Operated at Low Electrical Fields with High Strains

“…An area strain comparison of IL-elastomer 2 and previously reported dielectric elastomers was performed. As shown in Figure b and Table S6, IL-elastomer 2 undergoes a higher area strain in a relatively low electric field (<30 V/μm) than the commercial elastomer Sylgard 184 and most filler-modified and chemically modified PDMS elastomers. ,,,,,− Interestingly, IL-elastomer 2 achieved the 3 times higher actuation strain than the PDMS elastomer modified with polyaniline in a similar electric field. The high actuation strain of the novel IL-elastomer highlights the potential of the proposed strategy to prepare a high-performance actuator with difunctional IL.…”

“…However, reliable and reproducible fabrication of the dielectric films below 20 μm is challenging and costly with existing methodologies. Another way to prepare DEAs operating at low voltages is using soft elastomers, which can be prepared by, for example, reducing the crosslinking density or by crosslinking of bottle brush PDMS. , However, most DEAs suffer from a low level of tangible forces of the actuator due to the combination of both low Y and low ε r . Thus, focus in this work is on achieving large strain and low voltages by simultaneously increasing ε r and lowering Y with inclusion of ionic liquids (ILs) grafted to the polymer chains in order to avoid the ILs to migrate under the high electrical field.…”

“…However, reliable and reproducible fabrication of the dielectric films below 20 μm is challenging and costly with existing methodologies. Another way to prepare DEAs operating at low voltages is using soft elastomers, which can be prepared by, for example, reducing the crosslinking density 16 or by crosslinking of bottle brush PDMS. 17,18 However, most DEAs suffer from a low level of tangible forces of the actuator due to the combination of both low Y and low ε r .…”

All-Polymer Piezo-Composites for Scalable Energy Harvesting and Sensing Devices

“…Composite materials can act as electrostatic actuators with compliant electrodes deposited on the free-standing films when a direct current is applied, thanks to their dielectric nature. The capability of actuation of the composite samples was investigated in electromechanical tests using circular actuators, and the lateral actuation displacement was optically measured using a digital camera in order to evaluate the electrode extension [ 46 ]. An increasing voltage step was applied to the samples until a breakdown through the material occurred.…”

“…Circular electrodes of carbon black powder (8 mm in diameter) were deposited concentrically on both sides of the polymeric film. The lateral actuation displacement was optically measured using a digital camera and software in order to evaluate the electrode extension [ 46 ]. Static contact angle measurements were carried out using the sessile drop method at room temperature on a CAM-101 contact angle system from KSV Instruments, Helsinki, Finland.…”