Ruiz-Pardo Cinthya, Silva-Gutiérrez Luisa, Lizardi-Mendoza Jaime, López-Franco Yolanda, Peniche-Covas Carlos, Argüelles-Monal Waldo
Grupo de Investigación en Biopolímeros, Centro de Investigación en Alimentación y Desarrollo A.C., Hermosillo 83304, Sonora, Mexico.
Facultad de Química, Universidad de la Habana, Vedado, La Habana 10400, Cuba.
Polymers (Basel). 2022 Mar 16;14(6):1202. doi: 10.3390/polym14061202.
The Diels-Alder reaction is recognized to generate highly selective and regiospecific cycloadducts. In this study, we carried out a rheological and kinetic study of -furfuryl chitosan hydrogels based on the Diels-Alder click reaction with different poly(ethylene)glycol-maleimide derivatives in dilute aqueous acidic solutions. It was possible to prepare clear and transparent hydrogels with excellent mechanical properties. Applying the Winter and Chambon criterion the gel times were estimated at different temperatures, and the activation energy was calculated. The higher the temperature of gelation, the higher the reaction rate. The crosslinking density and the elastic properties seem to be controlled by the diffusion of the polymer segments, rather than by the kinetics of the reaction. An increase in the concentration of any of the two functional groups is accompanied by a higher crosslinking density regardless maleimide:furan molar ratio. The hydrogel showed an improvement in their mechanical properties as the temperature increases up to 70 °C. Above that, there is a drop in G' values indicating that there is a process opposing to the Diels-Alder reaction, most likely the retro-Diels-Alder.
狄尔斯-阿尔德反应被认为能生成高度选择性和区域特异性的环加成产物。在本研究中，我们在稀酸性水溶液中，基于狄尔斯-阿尔德点击反应，对含有不同聚乙二醇-马来酰亚胺衍生物的糠基壳聚糖水凝胶进行了流变学和动力学研究。制备出具有优异机械性能的透明水凝胶是可行的。应用温特和尚邦准则，在不同温度下估算了凝胶时间，并计算了活化能。凝胶化温度越高，反应速率越高。交联密度和弹性性能似乎由聚合物链段的扩散控制，而非反应动力学。无论马来酰亚胺与呋喃的摩尔比如何，两种官能团中任何一种浓度的增加都会伴随着更高的交联密度。随着温度升高至70°C，水凝胶的机械性能有所改善。高于该温度，G'值下降，表明存在与狄尔斯-阿尔德反应相反的过程，很可能是逆狄尔斯-阿尔德反应。
