Cai Zijing, Ji Bolin, Yan Kelu, Zhu Quan
College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China.
National Engineering Research Center for Dyeing and Finishing of Textiles, Donghua University, Shanghai 201620, China.
Polymers (Basel). 2019 Dec 12;11(12):2071. doi: 10.3390/polym11122071.
Cotton fabrics are prone to wrinkles and can be treated with citric acid (CA) to obtain good anti-wrinkle properties. However, the yellowing of the CA-treated fabrics is one big obstacle to the practical application of citric acid. The changing sequence order of CA anhydride and unsaturated acid (the reason for yellowing), such as aconitic acid (AA), has not been investigated. Herein, Fourier transform infrared (FTIR) spectroscopy, two-dimensional correlation spectroscopy (2Dcos), and Gaussian calculation were employed to characterize the reaction mechanism between CA with cellulose. FTIR spectra of the CA-treated fabrics heated under different temperatures were collected and further analyzed with 2Dcos. The results indicated the changing sequence order: 1656 cm→1784 cm→1701 cm, ("→" means earlier than), i.e., unsaturated acid→anhydride→ester. Moreover, a change of Gibbs free energy (ΔG) showed that trans-AA (ΔG = -22.10 kJ/mol) is more thermodynamically favorable to be formed than CA anhydride 1 (ΔG = -0.90 kJ/mol), which was proved by Gaussian computational modeling. By taking cellobiose as a model of cellulose, the ΔG results proved that O(6)-H(6) on the glucose ring is the most likely hydroxyl to react with anhydride originated from CA or AA, especially with the terminal carbonyl group.
棉织物容易起皱，可以用柠檬酸（CA）处理以获得良好的抗皱性能。然而，经CA处理的织物发黄是柠檬酸实际应用中的一大障碍。CA酸酐与不饱和酸（发黄的原因），如乌头酸（AA）的变化顺序尚未得到研究。在此，采用傅里叶变换红外（FTIR）光谱、二维相关光谱（2Dcos）和高斯计算来表征CA与纤维素之间的反应机理。收集了在不同温度下加热的经CA处理的织物的FTIR光谱，并用2Dcos进行了进一步分析。结果表明变化顺序为：1656 cm→1784 cm→1701 cm（“→”表示早于），即不饱和酸→酸酐→酯。此外，吉布斯自由能（ΔG）的变化表明，反式AA（ΔG = -22.10 kJ/mol）在热力学上比CA酸酐1（ΔG = -0.90 kJ/mol）更有利于形成，这一点通过高斯计算模型得到了证明。以纤维二糖作为纤维素的模型，ΔG结果证明葡萄糖环上的O(6)-H(6)是最有可能与源自CA或AA的酸酐反应的羟基，尤其是与末端羰基反应。
Zotero 插件
