Lu Yan-Na, Mo Kai, Liang Xue-Hang, Xie Jia-Sen, Yang Ying, Zheng Lin, Gu Mingwei, Liu Xiang-Ru, Lu Yunjie, Ge Jin
MOE Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510006, China.
ACS Appl Mater Interfaces. 2024 Nov 6;16(44):60992-61003. doi: 10.1021/acsami.4c12851. Epub 2024 Oct 23.
Ion-conductive hydrogels have received great attention due to their significant potential in flexible electronics. However, achieving hydrogels that simultaneously possess high ionic conductivity and stability under varying humidity conditions remains a challenge, limiting their practical applications. Herein, we propose a thermally controlled chemical cross-linking strategy to prepare an elastic and conductive hydrogel (ECH) of poly(vinyl alcohol) (PVA) with high content of HSO. The covalent cross-links formed effectively tackle the instability issue in high humidity of physically cross-linked PVA/HSO hydrogels with high ionic conductivity, which were previously developed via the polymer-in-salt strategy. We systematically investigated the reaction conditions and clarified the methods to optimize the hydroxyl dehydration of PVA, resulting in excellent mechanical properties and ion conductivity simultaneously. The ECH demonstrates impressive ionic conductivity (up to 392 ± 49 mS cm) and elasticity (over 80% resilience upon stretching and compression after being equilibrated at various humidity levels for 24 days). Thanks to the excellent water retention of the high HSO content, the ECH maintains an ionic conductivity exceeding 210 mS cm for over 420 days at 50% relative humidity (RH) and retains over 100 mS cm even after 3 days under extremely dry conditions (7% RH). These remarkable properties make the ECH an ideal candidate for applications requiring reliable ionic conductivity in diverse environmental conditions. Additionally, we demonstrated that the ECH can function as a stretchable Joule heater with high conformability for heating up objects with curved surfaces. The heating rate could reach a fast rate of ∼12 °C s even when a human-safe alternating current voltage is below 36 V, attributed to the high ionic conductivity. We believe that the high performance and ease of fabrication make our hydrogels a promising candidate for use as electrolytes in flexible energy storage devices, electrolyte gates in electrochemical transistors, and artificial skin, which often face long-term stability challenges under varying humidity conditions.
离子导电水凝胶因其在柔性电子学中的巨大潜力而备受关注。然而，制备在不同湿度条件下同时具有高离子导电性和稳定性的水凝胶仍然是一个挑战，这限制了它们的实际应用。在此，我们提出一种热控化学交联策略，以制备具有高含量HSO的聚（乙烯醇）（PVA）弹性导电水凝胶（ECH）。形成的共价交联有效地解决了先前通过盐中聚合物策略开发的具有高离子导电性的物理交联PVA/HSO水凝胶在高湿度下的不稳定性问题。我们系统地研究了反应条件，并阐明了优化PVA羟基脱水的方法，从而同时获得了优异的机械性能和离子导电性。ECH表现出令人印象深刻的离子导电性（高达392±49 mS cm）和弹性（在不同湿度水平下平衡24天后，拉伸和压缩后的回弹性超过80%）。由于高HSO含量具有出色的保水性，ECH在50%相对湿度（RH）下超过420天保持离子导电性超过210 mS cm，即使在极端干燥条件（7%RH）下3天后仍保持超过100 mS cm。这些卓越的性能使ECH成为在各种环境条件下需要可靠离子导电性的应用的理想候选材料。此外，我们证明ECH可以作为具有高贴合性的可拉伸焦耳加热器，用于加热具有曲面的物体。即使在低于36 V的人体安全交流电压下，加热速率也能达到约12 °C s的快速速率，这归因于高离子导电性。我们相信，高性能和易于制造使我们的水凝胶成为用作柔性储能装置中的电解质以及电化学晶体管中的电解质门和人造皮肤的有前途的候选材料，这些应用在不同湿度条件下经常面临长期稳定性挑战。
