The double-network (DN) structure is a state-of-the-art strategy used for toughening soft materials. The challenge for widespread applications, however, is the difficulty in synthesizing the two interpenetrating networks with contrasting architecture, i.e., one network is brittle and sparse and the other is stretchable and dense. Such structures are formed to toughen hydrogels via two-step sequential synthesis of a highly swellable polyelectrolyte network and a subsequent stretchable network in aqueous media; however, this approach is not directly applicable for fabricating tough DN elastomers from low-polar polymers. Herein, we propose a polyelectrolyte approach to fabricate tough solvent-free DN elastomers comprising a hybridized brittle polyelectrolyte network and a stretchable low-polar polyacrylic network. Because polyelectrolyte networks swell significantly in high-dielectric media, the contrasting DN structure can be fabricated using an organic cosolvent with an extremely high dielectric constant. By removing the solvent, we obtained polyelectrolyte–elastomeric polyacrylate DN elastomers, which exhibit a moderate elastic modulus (∼1 MPa), distinct yielding, high strength (∼5 MPa nominal stress), and large stretchability (∼2000% strain) accompanied by strain-hardening and high fracture toughness (∼10⁴ J m^–2). The volume ratio of the two networks is a key parameter governing mechanical performance. This approach broadens polymer choices for developing robust elastomers.

中文翻译：

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在非水介质中使用聚电解质的离子解离制备坚韧且可拉伸的混合双网弹性体

双网（DN）结构是用于增韧软材料的最新技术。然而，对于广泛应用的挑战是难以以对比的架构来合成两个互穿网络，即，一个网络是脆弱且稀疏的，而另一个则是可扩展且密集的。通过两步顺序合成高溶胀性聚电解质网络和随后在水性介质中的可拉伸网络，形成这种结构来增强水凝胶的韧性。但是，这种方法不能直接用于由低极性聚合物制造坚韧的DN弹性体。在这里，我们提出了一种聚电解质的方法来制造坚韧的无溶剂的DN弹性体，该弹性体包括混合的脆性聚电解质网络和可拉伸的低极性聚丙烯酸网络。由于聚电解质网络在高介电介质中会显着膨胀，因此可以使用介电常数极高的有机助溶剂来制造对比DN结构。通过除去溶剂，我们获得了聚电解质-弹性聚丙烯酸酯DN弹性体，该弹性体具有适度的弹性模量（〜1 MPa），屈服强度高，强度高（〜5 MPa标称应力）和大的可拉伸性（〜2000％应变），同时具有应变硬化和高断裂韧性（〜10⁴ J m ^–2）。两个网络的体积比是控制机械性能的关键参数。这种方法拓宽了用于开发坚固弹性体的聚合物选择。