Polymerization of Methyl Methacrylate with Lithium Triflate. A Kinetic and Structural Study

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• 作者：Laura Hermosilla ; Paloma Calle ; Pilar Tiemblo ; Nuria Garc铆a ; Leoncio Garrido ; Julio Guzm谩n
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：July 23, 2013
• 年：2013
• 卷：46
• 期：14
• 页码：5445-5454
• 全文大小：421K
• 年卷期：v.46,no.14(July 23, 2013)
• ISSN：1520-5835

文摘

The radical photopolymerization of methyl methacrylate in the presence of lithium triflate is investigated by EPR and NMR spectroscopies in order to assess the effect of the ionic medium on the polymerization kinetics. The EPR spectra show a notorious increase in the concentration of propagating radical as result of a dramatic decrease in the average termination rate coefficient. IR spectroscopy experiments and theoretical studies confirm the formation of a complex between the lithium cation and the oxygen atom at the carbonyl position of the ester in the methyl methacrylate. The electrostatic repulsion between the complexed propagating radicals, specifically at the end of the chains, allows explaining the observed low termination rate. This strong interaction would lead to 鈥渜uasi-living鈥?polymer chains from the first steps of the polymerization.