Effect of the ester side-chain on the propagation kinetics of alkyl methacrylates - An entropic or enthalpic effect?
Effect of the ester side-chain on the propagation kinetics of alkyl methacrylates - An entropic or enthalpic effect?
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酯侧链对甲基丙烯酸烷基酯传播动力学的影响 - 熵效应或焓效应？
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
G. Willett
中科院分区：
文献类型：
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作者：
M. Zammit;M. Coote;T. P. Davis;G. Willett
采用脉冲激光聚合技术（PLP）测定了苯乙烯（STY）、甲基丙烯酸甲酯（MMA）、甲基丙烯酸乙酯（EMA）、甲基丙烯酸正丁酯（BMA）和甲基丙烯酸苄酯（BzMA）的均相增长速率系数。特别注意通过尺寸排阻色谱法（SEC）与串联连接的在线低角激光散射（LALLS）、差示粘度计（DV）和差示折射率（DRI）检测器对PLP分布的分子量分析。使用两种不同的方法分析PLP分布：第一，通过Mark-Houwink-Sakurada（MHS）常数转换为通用校准曲线，第二，使用绝对检测方法直接分析分子量分布。并以实测的阿耳忒弥斯参数为参考，讨论了这两种方法的准确度和精度。增长速率系数与酯侧链尺寸的变化主要归因于指前因子。这与理论预测一致，但与PLP最近对该系列的研究相反。这种明显的矛盾的解释建议。
The technique of pulsed-laser polymerization (PLP) was used to measure homopropagation rate coefficients for styrene (STY), methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (BMA), and benzyl methacrylate (BzMA). Special attention was given to the molecular weight analysis of PLP distributions by size exclusion chromatography (SEC) with online low-angle laser- light scattering (LALLS), differential viscometry (DV), and differential refractive index (DRI) detectors connected in series. The PLP distributions were analyzed using two different approaches: first, by transformations to the universal calibration curve via Mark-Houwink-Sakurada (MHS) constants and, second, by direct analysis of the molecular weight distributions using absolute detection methods. The accuracy and precision of the two approaches is discussed with reference to the measured Arrhenius parameters. The variation in the propagation rate coefficients with ester side chain size is attributed primarily to the preexponential factor. This is consistent with theoretical predictions but in opposition to a recent PLP study of this series. An explanation for this apparent contradiction is suggested.