Computational Study of Cyclohexanone鈥揗onomer Co-initiation Mechanism in Thermal Homo-polymerization of Methyl Acrylate and Methyl Methacrylate

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• 作者：Shi Liu ; Sriraj Srinivasan ; Michael C. Grady ; Masoud Soroush ; Andrew M. Rappe
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：June 7, 2012
• 年：2012
• 卷：116
• 期：22
• 页码：5337-5348
• 全文大小：652K
• 年卷期：v.116,no.22(June 7, 2012)
• ISSN：1520-5215

文摘

This paper presents a systematic computational study of the mechanism of cyclohexanone鈥搈onomer co-initiation in high-temperature homopolymerization of methyl acrylate (MA) and methyl methacrylate (MMA). Previous experimental studies of spontaneous thermal homopolymerization of MA and MMA showed higher monomer conversion in the presence of cyclohexanone than xylene. However, these studies did not reveal the initiation mechanism(s) or the initiating species. To identify the initiation mechanism and the initiating species, we explore four different mechanisms, (1) Kaim, (2) Flory, (3) 伪-position hydrogen transfer, and (4) Mayo, using first-principles density functional theory (DFT) and second-order M酶ller鈥揚lesset perturbation theory (MP2) calculations. Transition-state geometries for each mechanism are determined using B3LYP/6-31G* and assessed with MP2/6-31G*. Activation energies and rate constants are calculated using transition-state theory. The harmonic oscillator approximation and tunneling corrections are applied to compute the reaction rate constants. This study indicates that 伪-position hydrogen transfer and Mayo mechanisms have comparable barriers and are capable of generating monoradicals for initiating polymerization of MA and MMA; these two mechanisms can cause cyclohexanone鈥搈onomer co-initiation in thermal polymerization of MA and MMA.