Abstract Hydrophobic long carbon chains (C16) were grafted onto the main chains of Xanthan Gum by etherification under the ordered conformation of Xanthan. Rheology and pyrene fluorescence spectroscopy experiments discovered that the critical association concentration (CAC) of modified Xanthan solution was 0.16%, and ANS fluorescence probe test indicated modified Xanthan had better hydrophobic association effect than before. Additionally, macroscopic and microscopic properties of modified Xanthan solutions, as well as the effects of temperature and salt on its association behavior were explored by rheology and scanning electron microscopy (SEM), revealed the reason of the improvement of modified Xanthan properties in micro levels. The results show that the modified Xanthan had better high-temperature resistance, which retained 421 mPa·s at 140 °C, about four times the apparent viscosity of Xanthan before modification (125 mPa·s). Adding NaCl up to the salt concentration of 4.0%, modified Xanthan still maintained well spatial network structure and a high apparent viscosity (728 mPa·s), while the apparent viscosity of Xanthan before modification was much lower than 728 mPa·s. Since the hydrophobically modification didn’t change the structure of Xanthan, the improvement of the above properties all came from the contribution of hydrophobic chain graft. Graphical Abstract

中文翻译：

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疏水改性黄原胶XG-C16的制备及性能评价

摘要 在黄原胶的有序构象下，疏水性长碳链（C16）通过醚化接枝到黄原胶的主链上。流变学和芘荧光光谱实验发现，改性黄原胶溶液的临界缔合浓度(CAC)为0.16%，ANS荧光探针测试表明改性黄原胶比以前具有更好的疏水缔合效果。此外，通过流变学和扫描电子显微镜 (SEM) 探索了改性黄原胶溶液的宏观和微观性质，以及温度和盐分对其缔合行为的影响，揭示了改性黄原胶性能在微观水平上改善的原因。结果表明，改性黄原胶具有较好的耐高温性能，在 140 ℃保持 421 mPa·s，大约是改性前黄原胶表观粘度 (125 mPa·s) 的四倍。添加NaCl至4.0%的盐浓度，改性黄原胶仍保持良好的空间网络结构和较高的表观粘度（728 mPa·s），而改性前黄原胶的表观粘度远低于728 mPa·s。由于疏水改性并没有改变黄原胶的结构，因此上述性能的改善都来自疏水链接枝的贡献。图形概要 而改性前黄原胶的表观粘度远低于728 mPa·s。由于疏水改性并没有改变黄原胶的结构，因此上述性能的改善都来自疏水链接枝的贡献。图形概要 而改性前黄原胶的表观粘度远低于728 mPa·s。由于疏水改性并没有改变黄原胶的结构，因此上述性能的改善都来自疏水链接枝的贡献。图形概要