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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Study of Polymerization Mechanism of p-Xylylene Based Polymers
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Theoretical Study of Polymerization Mechanism of p-Xylylene Based Polymers

机译：对亚二甲苯基聚合物聚合机理的理论研究

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摘要

The mechanism of polymerization of p-xylylene and its derivatives is analyzed at the theoretical level. The polymerization reaction takes place in vacuo without any catalyst. The first step is a pyrolytic decomposition of starting material for polymerization, p-cyclophane, a cyclic dimer of p-xylylene, into biradical linear dimer and finally into two quinonoid monomeric molecules of p-xylylene. The quinonoid monomer is diamagnetic; i.e., it has a singlet ground state. The monomers after pyrolysis, when the temperature is lowered, do not re-form cyclic dimers but instead polymerize into long chain molecules. The initiation of polymerization requires dimerization of two monomers leading to formation of a genuine noncoupled biradical dimer. The chain molecules grow through the propagation reaction only one unit at a time, by the attachment of a monomer to a radical chain end. In this work the pyrolysis reaction, the initiation reaction and the first propagation steps of parylene polymerization (up to pentamer) are studied in details using different quantum chemical methods: AM1 and PM6 semiempirical methods and density functional theory (DFT) approach using B3LYP functional with two basis sets of different size (SVP and TZVP).
机译：在理论上分析了对二甲苯及其衍生物的聚合机理。聚合反应在没有任何催化剂的情况下在真空中进行。第一步是将用于聚合的起始原料对亚环芳基（对二甲苯的环状二聚体）热解为双自由基线性二聚体，最后分解为对二甲苯的两个醌型单体分子。醌类单体是反磁性的;也就是说，它具有单重态基态。热解后的单体，当温度降低时，不会重新形成环状二聚体，而是聚合成长链分子。聚合反应的引发需要两种单体的二聚化，从而形成真正的非偶联双自由基二聚体。通过单体与自由基链末端的连接，链分子一次仅通过一个单元通过传播反应生长。在这项工作中，使用不同的量子化学方法详细研究了聚对二甲苯聚合的热解反应，引发反应和第一步扩散步骤（直至五聚体）：AM1和PM6半经验方法以及使用B3LYP官能团的密度泛函理论（DFT）方法。两个不同大小的基础集（SVP和TZVP）。

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