Perju Elena, Shova Sergiu, Opris Dorina M
Laboratory for Functional Polymers, Swiss Federal Laboratories for Materials Science and Technology Empa, Ueberlandstr. 129, CH-8600 Dübendorf, Switzerland.
"Petru Poni" Institute of Macromolecular Chemistry of Romanian Academy, Aleea Gr. Ghica Voda, 41A, 700487 Iasi, Romania.
ACS Appl Mater Interfaces. 2020 May 20;12(20):23432-23442. doi: 10.1021/acsami.0c03692. Epub 2020 May 8.
The synthesis of novel dielectric elastomers that show a muscle-like actuation when exposed to a low electric field represents a major challenge in materials science. Silicone elastomers modified with polar side groups are among the most attractive dielectrics for such a purpose because of their high polarizability over a wide temperature and frequency range. Nitroaniline (NA) has a strong dipole moment, and therefore, its incorporation into silicone networks should allow the formation of elastomers with increased dielectric permittivity. However, incorporation of a large amount of NA into silicone needed to increase the dielectric permittivity is still challenging. In this work, we present the synthesis of polysiloxane elastomers modified with a large fraction of the nitroaniline (NA) polar group, following two different synthetic strategies. Both approaches allowed the formation of homogenous elastomers at the molecular level. These yellowish materials have a dielectric permittivity three times higher as compared to the reported NA-modified silicones. Additionally, they have excellent mechanical properties with low viscoelastic losses and a strain at break reaching 300%. Furthermore, the mechanical properties of these elastomers can be easily tuned by the content of cross-linkers used. The developed elastomers are highly stable in electromechanical tests and show an actuation strain of 8% at unprecedentedly low electric fields of 7.5 V/μm. The combination of properties such as high dielectric permittivity, large strain at break, low viscoelastic losses, fast and reversible actuation, and actuation at low electric fields is crucial for the new generation of dielectric elastomer materials that will find their way in applications ranging from artificial muscles, soft robots, sensors, and haptic displays to electronic skin.
合成在低电场下表现出类似肌肉驱动的新型介电弹性体是材料科学中的一项重大挑战。用极性侧基改性的有机硅弹性体因其在宽温度和频率范围内具有高极化率，是实现这一目的最具吸引力的电介质之一。硝基苯胺（NA）具有很强的偶极矩，因此，将其引入有机硅网络应能形成介电常数增加的弹性体。然而，要增加介电常数而将大量NA引入有机硅中仍然具有挑战性。在这项工作中，我们采用两种不同的合成策略，介绍了用大部分硝基苯胺（NA）极性基团改性的聚硅氧烷弹性体的合成。两种方法都能在分子水平上形成均匀的弹性体。这些淡黄色材料的介电常数比已报道的NA改性有机硅高三倍。此外，它们具有优异的机械性能，粘弹性损失低，断裂应变达到300%。此外，这些弹性体的机械性能可以通过所用交联剂的含量轻松调节。所开发的弹性体在机电测试中高度稳定，在7.5 V/μm的前所未有的低电场下显示出8%的驱动应变。高介电常数、大断裂应变、低粘弹性损失、快速可逆驱动以及在低电场下驱动等性能的组合，对于新一代介电弹性体材料至关重要，这些材料将在从人造肌肉、软机器人、传感器、触觉显示器到电子皮肤等各种应用中得到应用。
