A thermo-reversible sol–gel transition in solutions made of titanium n-butoxide, ethanol, water, and nitric acid is studied by in situ temperature-dependent Fourier transform infrared spectroscopy. Infrared spectra show that at temperatures departing from 45 °C, the nitrate ion substitutes the partially hydrolyzed butoxide ligands, by forming bridges and mono- and bidentate chelates. The exposed oxygen atoms in the nitrate ion favor the assembly between oligomers of low molecular weight through hydrogen bonds where water molecules work as binding agents, leaving to the gel formation. When the material returns to room temperature, the nitrate ion comes back to its free state, regenerating the sol. The suspension evolves with aging time from transparent to white, indicating the formation of TiO₂ particles, although the thermo-reversible effect is still observed upon heating. Infrared results suggest that gel formation proceeds through the same mechanism, however, the chelates and bridges occur through exposed Ti–OH moieties onto the particle surfaces. Additionally, after an aging period, a gel is formed at room temperature, that recovers the fluid state upon mechanical perturbation. In this case, TiO₂ particles join directly by week interactions such as hydrogen bonds. The dynamic rheological studies of the temperature-dependent viscoelastic behavior indicate that the elastic component is the most important in the material’s structure.

通过原位温度相关傅里叶变换红外光谱研究了由正丁醇钛、乙醇、水和硝酸制成的溶液中的热可逆溶胶-凝胶转变。红外光谱显示，在 45 °C 以外的温度下，硝酸根离子通过形成桥和单齿和双齿螯合物取代部分水解的丁醇配体。硝酸根离子中暴露的氧原子有利于低分子量低聚物之间通过氢键组装，其中水分子作为粘合剂起作用，从而形成凝胶。当材料恢复到室温时，硝酸根离子恢复到自由状态，使溶胶再生。悬浮液随老化时间由透明变为白色，表明形成了TiO ₂颗粒，尽管在加热时仍然观察到热可逆效应。红外结果表明凝胶形成通过相同的机制进行，然而，螯合物和桥通过暴露在颗粒表面上的 Ti-OH 部分发生。此外，经过一段时间的老化后，会在室温下形成凝胶，在机械扰动时恢复流体状态。在这种情况下，TiO ₂颗粒通过诸如氢键之类的周相互作用直接结合。随温度变化的粘弹性行为的动态流变学研究表明，弹性成分在材料结构中是最重要的。