Natural rubber (NR)/hexagonal mesoporous silica (HMS) nanocomposites (NRHMS) with enhanced thermal and hydrophobic properties were facilely prepared via in situ sol-gel formation with pH adjustment using a low sulphuric acid (H2SO4) acid concentration. The effect of the amount of 0.5 M H2SO4 (2.5-10 g) added into the pre-synthesis mixture on the physicochemical properties of the obtained NRHMS nanocomposites was investigated. With a small addition of H2SO4 solution, the fabricated NRHMS nanocomposite possessed an improved wormhole-like mesostructure arrangement with a thicker silica wall, which retarded the thermal decomposition of the NR phase, as deduced from the auto-oxidation of NR by thermogravimetric analysis. The H2O adsorption-desorption measurement revealed an increased hydrophobicity of the NRHMS composites, explained by the acid-catalyzed bridging of free silanol groups to siloxane bonds, which was supported by the X-ray photoelectron spectroscopy analysis. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy elemental mapping revealed a good dispersion of the NR phase within the mesostructured silica. However, a high amount of added H2SO4 solution led to silica-NR phase separation due to the decreased hydrophobic interaction between the silica precursor and rubber chain, as well as an agglomeration of the NR phase itself. The mechanism of NRHMS nanocomposite formation under pH-controlled conditions was proposed to proceed via a cooperative self-assembly route.

中文翻译：

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介孔结构天然橡胶/二氧化硅纳米复合材料的便捷制造，具有增强的热稳定性和疏水性。

通过使用低硫酸（H2SO4）酸浓度进行pH调节的原位溶胶-凝胶形成方法，可以轻松制备具有增强的热和疏水性的天然橡胶（NR）/六方介孔二氧化硅（HMS）纳米复合材料（NRHMS）。研究了预合成混合物中添加的0.5 M H2SO4（2.5-10 g）的量对所得NRHMS纳米复合材料理化性质的影响。少量添加H2SO4溶液，制成的NRHMS纳米复合材料具有改进的蠕虫状介孔结构，具有较厚的二氧化硅壁，这可以阻止NR相的热分解，这是通过热重分析法从NR的自氧化作用得出的。H2O吸附-解吸测量显示NRHMS复合材料的疏水性增加，X射线光电子能谱分析支持了游离硅烷醇基团与硅氧烷键的酸催化桥联反应。具有能量色散X射线光谱学的元素分析的扫描透射电子显微镜显示出NR相在介孔结构二氧化硅内良好的分散。但是，由于二氧化硅前体和橡胶链之间的疏水相互作用降低以及NR相本身的团聚，大量添加的H2SO4溶液导致了二氧化硅-NR相的分离。提出了在pH受控条件下NRHMS纳米复合物形成的机理，是通过协同自组装途径进行的。具有能量色散X射线光谱学的元素分析的扫描透射电子显微镜显示出NR相在介孔结构二氧化硅内良好的分散。但是，由于二氧化硅前体和橡胶链之间的疏水相互作用降低以及NR相本身的团聚，大量添加的H2SO4溶液导致了二氧化硅-NR相的分离。提出了在pH受控条件下NRHMS纳米复合物形成的机理，是通过协同自组装途径进行的。具有能量色散X射线光谱学的元素分析的扫描透射电子显微镜显示出NR相在介孔结构二氧化硅内良好的分散。但是，由于二氧化硅前体和橡胶链之间的疏水相互作用降低以及NR相本身的团聚，大量添加的H2SO4溶液导致了二氧化硅-NR相的分离。提出了在pH受控条件下NRHMS纳米复合物形成的机理，是通过协同自组装途径进行的。以及NR相本身的凝聚。提出了在pH受控条件下NRHMS纳米复合物形成的机理，是通过协同自组装途径进行的。以及NR相本身的凝聚。提出了在pH受控条件下NRHMS纳米复合物形成的机理，是通过协同自组装途径进行的。