Junliang Zhang#, Chenyang Tang#, Qingqing Kong, Mukun He, Peng Lv, Hua Guo, Yongqiang Guo, Xuetao Shi and Junwei Gu*. Strong and tough polyvinyl alcohol hydrogels with high intrinsic thermal conductivity. Soft Science, 2025, 5: 9.
http://dx.doi.org/10.20517/ss.2024.72
Abstract
Although polyvinyl alcohol (PVA) hydrogels display huge potential in tissue engineering, flexible and wearable electronic devices and soft robotics, their low intrinsic thermal conductivity and weak mechanical properties severely limit their wider applications in these areas. Herein, a Hofmeister effect-assisted “directional freezing-stretching” tactic is employed for simultaneously enhancing the intrinsic thermal conduction and mechanical properties of PVA hydrogels. The hydrogels are obtained through directional freezing followed by salting-out treatment and subsequent mechanical stretching and salting-out (DFS). The DFS PVA hydrogel with 15 wt% of PVA and a stretching ratio of 4 (DFS4) exhibits the highest thermal conductivity of 1.25 W/(m·K), which is 2.4 and 2.8 times that of PVA hydrogel prepared through frozen-thawed (FT) [0.52 W/(m·K)] and frozen-salted out (FS) [0.45 W/(m·K)] methods, respectively. The DFS4 PVA hydrogel also possesses greatly improved mechanical performances, exhibiting an elongation at break of 163.1%. In addition, the tensile strength, toughness, and elastic modulus of DFS4 PVA hydrogel significantly increase to 27.1 MPa, 25.3 MJ·m-3, and 21.5 MPa from 0.4 MPa, 0.32 MJ·m-3, and 0.07 MPa for FT PVA hydrogels, respectively. It is elucidated that the salting-out effect generates hydrophobic and crystalline regions, while directional freezing and stretching enhance the chain orientation in the DFS strategy. These effects synergistically contribute to the improvement of thermal conductivity and mechanical properties of PVA hydrogels.
聚乙烯醇（PVA）水凝胶在组织工程、柔性可穿戴电子设备和软机器人等领域具有巨大的应用潜力。然而，PVA水凝胶本征导热性能低且力学性能差，制约了其在更广领域的进一步发展和应用。本文基于Hofmeister效应，通过“定向冷冻-盐析-机械拉伸-盐析”（DFS）策略制备DFS PVA水凝胶，同步提升PVA水凝胶的本征导热性能和力学性能。当PVA质量分数为15 wt%且拉伸倍数为4（DFS4）时，DFS PVA水凝胶具有最高的本征导热性能，其导热系数为1.25 W/(m·K)，分别是基于冷冻解冻法（FT）和冷冻盐析法（FS）制备的FT PVA水凝胶[0.52 W/(m·K)]和FS PVA水凝胶[0.45 W/(m·K)]的2.4倍和2.8倍。此外，DFS4 PVA水凝胶的力学性能大幅提升，其断裂伸长率为163.1%。同时，DFS4 PVA水凝胶的拉伸强度、韧性和弹性模量分别从FT PVA水凝胶的0.4 MPa、0.32 MJ·m-3和0.07 MPa提高至27.1 MPa、25.3 MJ·m-3和21.5 MPa。研究表明，盐析效应能够促进PVA水凝胶中形成疏水区和结晶区，同时定向冷冻和机械拉伸会提升PVA分子链的取向度，这些效应协同提高了PVA水凝胶的导热性能和力学性能。
论文亮点
1. 基于Hofmeister效应，通过“定向冷冻-盐析-机械拉伸-盐析”策略，同步提升PVA水凝胶的本征导热性能和力学性能。
2. 当PVA质量分数为15 wt%且拉伸倍数为4时，DFS PVA水凝胶具有最高的本征导热性能，其导热系数为1.25 W/(m·K)，分别是FT PVA水凝胶[0.52 W/(m·K)]和FS PVA水凝胶[0.45 W/(m·K)]的2.4倍和2.8倍。
3. DFS4 PVA水凝胶的拉伸强度、韧性和弹性模量分别从FT PVA水凝胶的0.4 MPa、0.32 MJ·m-3和0.07 MPa提高至27.1 MPa、25.3 MJ·m-3和21.5 MPa。
第一作者：张军亮邮件地址：junliang.zhang@nwpu.edu.cn
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