EDC/NHS activation mechanism of polymethacrylic acid: anhydride versus NHS-ester 机翻标题: 暂无翻译,请尝试点击翻译按钮。

来源
RSC Advances
年/卷/期
2015 / 5 / 86
页码
69939-69947
作者单位
Nanjing Univ, Sch Chem & Chem Engn, State Key Lab Coordinat Chem, Nanjing 210093, Jiangsu, Peoples R China;Nanjing Univ, Sch Chem & Chem Engn, State Key Lab Coordinat Chem, Nanjing 210093, Jiangsu, Peoples R China;Nanjing Univ, Sch Chem & Chem Engn, State Key Lab Coordinat Chem, Nanjing 210093, Jiangsu, Peoples R China;Nanjing Univ, Sch Chem & Chem Engn, State Key Lab Coordinat Chem, Nanjing 210093, Jiangsu, Peoples R China;Nanjing Univ, Sch Chem & Chem Engn, State Key Lab Coordinat Chem, Nanjing 210093, Jiangsu, Peoples R China;
作者
Yan, Qin;Zheng, Hong-Ning;Jiang, Chuan;Li, Kun;Xiao, Shou-Jun;
摘要
Polymer brushes of polymethacrylic acid (PMAA) and PMAA-associated polymer blends of PMAA/PNIPAM (poly-N-isopropylacrylamide) were prepared on porous silicon for further investigation of the EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide) activation mechanisms by infrared spectroscopy. When the fragmentation degree of PMAA blocks in PMAA-associated polymer blends is increased, the production of anhydride wanes from dominant to recessive, whereas a complementary product of the NHS-ester waxes from recessive to dominant. The Thorpe-Ingold effect was applied to explain the formation of anhydride: the gem-dialkyl groups of PMAA next to the carboxylic acids compress the acid side chains close to each other; thus, once the intermediate of O-acylisourea forms, it will be attacked by the intramolecular neighboring acid much faster than any other nucleophiles such as NHS and water, and therefore the six-membered ring of the anhydride will be formed. All acid side chains in PMAA standing next to each other will form an anhydride, primarily due to the Thorpe-Ingold effect, unless they are sterically hindered, whereas only isolated acid side chains form the NHS-ester. The EDC/NHS activation results for four small molecules of dicarboxylic acids in aqueous media, namely, glutaric acid and 2,2-dimethyl glutaric acid, which generate disuccinimidyl ester with high yield, and succinic acid and 2,2-dimethyl succinic acid, which remain intact, can also be explained by the Thorpe-Ingold effect. A clear understanding of the EDC/NHS activation mechanisms of PMAA will take us a step closer for resolving the mechanistic ambiguity of the carbodiimide/additive coupling reactions for amide bond formation.
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