Ghriga Mohammed Abdelfetah, Khoukh Abdelouahed, Lebouachera Seif El Islam, Grassl Bruno
Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, (Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les matériaux), 2 Avenue P. Angot, Technopole Hélioparc, 64000 Pau, France.
Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, Total Energies, LFCR, Parc Montaury, Anglet, France.
Soft Matter. 2022 Sep 28;18(37):7075-7081. doi: 10.1039/d2sm00996j.
Since the introduction of polyethylenimine (PEI)/acrylamide-based polymer gel systems in the late 90's, the literature knowledge on the crosslinking mechanisms between the various polymers (PAM, PHPA, and PatBA) and the crosslinker (PEI) was only limited to observations on gelation times and gel strength variations compared to other gel systems. In this paper, classic proton and carbon nuclear magnetic resonance "NMR" experiments and advanced 2D DOSY and NOESY techniques were employed for studying the interactions between the amine groups of PEI and amide or carboxylate groups of partially hydrolysed polyacrylamide (PHPA). Among the many possibilities, we showed that the interaction occurring during thermogelation is mainly due to covalent bonding. The latter results from a transamidification reaction between the polymer amide groups and the primary amines of the crosslinker. The reaction, at high temperatures, was accompanied by some hydrolysis of the polymer amide groups. Consequently, the kinetics of the reaction and hydrolysis were evaluated and fitted using pseudo first-order equations where the hydrolysis kinetics was found to be three times lower than that of the reaction.
自20世纪90年代末引入基于聚乙烯亚胺（PEI）/丙烯酰胺的聚合物凝胶体系以来，与其他凝胶体系相比，关于各种聚合物（聚丙烯酰胺、部分水解聚丙烯酰胺和聚丙烯酸丁酯）与交联剂（PEI）之间交联机制的文献知识仅局限于对凝胶化时间和凝胶强度变化的观察。在本文中，采用经典的质子和碳核磁共振“NMR”实验以及先进的二维扩散排序谱（DOSY）和核欧沃豪斯效应谱（NOESY）技术，研究PEI的胺基与部分水解聚丙烯酰胺（PHPA）的酰胺基或羧基之间的相互作用。在众多可能性中，我们表明热凝胶化过程中发生的相互作用主要是由于共价键合。后者是由聚合物酰胺基与交联剂的伯胺之间的转酰胺反应产生的。在高温下，该反应伴随着聚合物酰胺基的一些水解。因此，使用伪一级方程对反应和水解的动力学进行了评估和拟合，发现水解动力学比反应动力学低三倍。
