Transesterification and epoxide ring-opening reactions are two mechanism routes that explain chemical modifications of macromolecules by glycidyl methacrylate (GMA). Although the coupling reaction of the GMA with macromolecules has widely been investigated, there are still mechanisms that remain to be explained when GMA is processed in an aqueous solution at different pH conditions. To this end, reaction mechanisms of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) by GMA in water in acidic and basic conditions were investigated thoroughly. The presence of hydroxyl groups in PVA and carboxyl groups in PAAc allowed for a better evaluation of the reaction mechanisms. The analysis of the ¹H and ¹³C NMR spectra clearly demonstrated that the chemical reactions of GMA with carboxyl groups and alcohols of the macromolecules in an aqueous solution are dependent on pH conditions. At pH 3.5, the GMA reacts with both the carboxylic and the hydroxyl groups through an epoxide ring-opening mechanism. At pH 10.5, the GMA undergoes a hydrolysis process and reacts with hydroxyl groups by way of both the transesterification and the epoxide ring-opening mechanisms, whereas the ring-opening reaction is the preferential pathway.

中文翻译：

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甲基丙烯酸缩水甘油酯在聚乙烯醇和聚丙烯酸的羟基和羧基上的反应：这个反应机理还不清楚吗？

酯交换反应和环氧化物开环反应是两种机理路线，它们解释了甲基丙烯酸缩水甘油酯（GMA）对大分子的化学修饰。尽管已经广泛研究了GMA与大分子的偶联反应，但是当在不同pH条件下在水溶液中处理GMA时，仍然有待解释的机理。为此，彻底研究了在酸性和碱性条件下，GMA在水中对聚乙烯醇（PVA）和聚丙烯酸（PAAc）的反应机理。PVA中存在羟基，PAAc中存在羧基，可以更好地评估反应机理。¹ H和¹³的分析1 H NMR光谱清楚地表明，在水溶液中GMA与大分子的羧基和醇的化学反应取决于pH条件。在pH 3.5时，GMA通过环氧开环机制与羧基和羟基反应。在pH 10.5时，GMA经历水解过程，并通过酯基转移和环氧化物的开环机制与羟基反应，而开环反应是优先途径。