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）水凝膠在組織工程、柔性可穿戴電子設備和軟機器人等領域具有巨大的應用潛力。然而，PVA水凝膠本征導熱性能低且力學性能差，制約了其在更廣領域的進一步發展和應用。本文基于Hofmeister效應，通過“定向冷凍-鹽析-機械拉伸-鹽析”（DFS）策略制備DFS PVA水凝膠，同步提升PVA水凝膠的本征導熱性能和力學性能。當PVA質量分數為15 wt%且拉伸倍數為4（DFS4）時，DFS PVA水凝膠具有最高的本征導熱性能，其導熱系數為1.25 W/(m·K)，分別是基于冷凍解凍法（FT）和冷凍鹽析法（FS）制備的FT PVA水凝膠[0.52 W/(m·K)]和FS PVA水凝膠[0.45 W/(m·K)]的2.4倍和2.8倍。此外，DFS4 PVA水凝膠的力學性能大幅提升，其斷裂伸長率為163.1%。同時，DFS4 PVA水凝膠的拉伸強度、韌性和彈性模量分別從FT PVA水凝膠的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，鹽析效應能夠促進PVA水凝膠中形成疏水區和結晶區，同時定向冷凍和機械拉伸會提升PVA分子鏈的取向度，這些效應協同提高了PVA水凝膠的導熱性能和力學性能。
論文亮點
1. 基于Hofmeister效應，通過“定向冷凍-鹽析-機械拉伸-鹽析”策略，同步提升PVA水凝膠的本征導熱性能和力學性能。
2. 當PVA質量分數為15 wt%且拉伸倍數為4時，DFS PVA水凝膠具有最高的本征導熱性能，其導熱系數為1.25 W/(m·K)，分別是FT PVA水凝膠[0.52 W/(m·K)]和FS PVA水凝膠[0.45 W/(m·K)]的2.4倍和2.8倍。
3. DFS4 PVA水凝膠的拉伸強度、韌性和彈性模量分別從FT PVA水凝膠的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：張軍亮郵件地址：junliang.zhang@nwpu.edu.cn
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