Hydrogels with high mechanical strength are essential for its most industrial applications. In this work, the hydrophobic SiO₂ nanoparticles (M-SiO₂ NPs) modified with octadecyltrimethoxysilane were used as physical crosslinker to toughen the mechanical properties of hydrogels. The solution of monomers containing M-SiO₂ NPs, N-hydroxymethyl acrylamide (NHAM), acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), was polymerized to prepare a P(NHAM/AA/AMPS)-based composite hydrogel without any chemical cross-linker. The composition and microstructure of the hydrogel were carefully studied with Fourier transform infrared spectroscopy and scanning electron microscopy. The mechanical properties of the hydrogel were investigated through compressive and tensile tests. Dynamic swelling tests were carried out at different pH values (1.0–12.0) and salinity (2000–20,000 mg/L) to study the acid resistance, alkali resistance, and salt resistance of the hydrogel. The obtained results showed that the hydrogel exhibited excellent mechanical performance, which was attributed to the unique 3D network formed by the hydrogen bond between M-SiO₂ NPs and polymer as well as the hydrophobic association effect between the hydrophobic chains of M-SiO₂ NPs. Furthermore, the hydrophobic association effect was enhanced when contacting with salt, acid, and alkali solutions, thus endowing the hydrogel with intensified salt resistance and wider acid–base adaptability range.

中文翻译：

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疏水改性纳米二氧化硅提高P(N-羟甲基丙烯酰胺/丙烯酸/2-丙烯酰胺-2-甲基丙磺酸)水凝胶的力学性能

具有高机械强度的水凝胶对其大多数工业应用至关重要。在这项工作中，用十八烷基三甲氧基硅烷改性的疏水性SiO ₂纳米颗粒（M-SiO ₂ NPs）作为物理交联剂来增强水凝胶的机械性能。含有M-SiO _{2的单体溶液}将 NPs、N-羟甲基丙烯酰胺 (NHAM)、丙烯酸 (AA)、2-丙烯酰胺基-2-甲基丙磺酸 (AMPS) 聚合制备无任何化学交联的 P(NHAM/AA/AMPS) 基复合水凝胶链接器。用傅里叶变换红外光谱和扫描电子显微镜仔细研究了水凝胶的组成和微观结构。通过压缩和拉伸试验研究了水凝胶的机械性能。在不同pH值（1.0-12.0）和盐度（2000-20,000 mg/L）下进行动态溶胀试验，研究水凝胶的耐酸、耐碱和耐盐性能。所得结果表明，水凝胶表现出优异的机械性能，这归因于由 M-SiO 之间的氢键形成的独特的 3D 网络。₂ NPs与聚合物以及M-SiO ₂ NPs疏水链之间的疏水缔合效应。此外，与盐、酸和碱溶液接触时疏水缔合效应增强，从而赋予水凝胶更强的耐盐性和更宽的酸碱适应范围。