In this work, we report the formation of a novel, aqueous-based thermo-responsive, supramolecular gelling system prepared by a convenient and efficient self-assembly of a long-chain amino-amide and citric acid. To determine the viscosity behavior and to gain insights into the gelation mechanism, a complementary combination of techniques, including Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic light scattering (DLS), and sinusoidal oscillatory tests, were used. The supramolecular gelator exhibited remarkably reversible sol–gel transitions induced by temperature at 76 °C. At a concentration of 5 wt%, the zero-frequency viscosity of the supramolecular system increased by about four orders of magnitude (from 4.2 to 12 563 Pa s) by changing the temperature from 23 °C to 76 °C. The viscous nature of the supramolecular gel could be preserved up to 90 °C. The synergistic combination of the hydrogen bonding between amino and carboxylic acid groups and the electrostatic interactions arising from the protonation of the amino-group and the deprotonation of carboxylic acid groups enhanced at higher temperatures is presumably responsible for the thermo-responsive behavior. We anticipate that these supramolecular gelators can be beneficial in various applications such as hydrogel scaffolds for regenerative medicine, personal care products and cosmetics, and enhanced oil recovery as viscosity modifiers.

中文翻译：

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基于酰胺基胺和柠檬酸的超分子组装的热敏凝胶†

在这项工作中，我们报告了一种新型的，基于水的热响应性，超分子胶凝体系的形成，该体系是通过长链氨基酰胺和柠檬酸的便捷有效的自组装而制备的。为了确定粘度行为并深入了解胶凝机理，使用了多种技术的互补组合，包括傅里叶变换红外光谱（FTIR），差示扫描量热法（DSC），动态光散射（DLS）和正弦振荡测试。超分子胶凝剂表现出由76°C的温度诱导的可逆的溶胶-凝胶转变。在5 wt％的浓度下，通过将温度从23°C更改为76°C，超分子系统的零频粘度增加了大约四个数量级（从4.2到12 563 Pa s）。超分子凝胶的粘性性质可以保持到90°C。推测氨基和羧酸基团之间的氢键与由氨基的质子化和在更高的温度下增强的羧酸基团的去质子化所产生的静电相互作用的协同组合是热响应行为的原因。我们预计这些超分子胶凝剂在各种应用中将是有益的，例如用于再生医学的水凝胶支架，个人护理产品和化妆品，以及作为粘度调节剂的提高的采油率。推测氨基和羧酸基团之间的氢键与由氨基的质子化和在更高的温度下增强的羧酸基团的去质子化所产生的静电相互作用的协同组合是热响应行为的原因。我们预计这些超分子胶凝剂在各种应用中将是有益的，例如用于再生医学的水凝胶支架，个人护理产品和化妆品，以及作为粘度调节剂的提高的采油率。推测氨基和羧酸基团之间的氢键与由氨基的质子化和在更高的温度下增强的羧酸基团的去质子化所产生的静电相互作用的协同组合是热响应行为的原因。我们预计这些超分子胶凝剂在各种应用中将是有益的，例如用于再生医学的水凝胶支架，个人护理产品和化妆品，以及作为粘度调节剂的提高的采油率。