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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Numerical Simulation of the Kinetics of Radical Decay in Single-Pulse High-Energy Electron-Irradiated Polymer Aqueous Solutions
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Numerical Simulation of the Kinetics of Radical Decay in Single-Pulse High-Energy Electron-Irradiated Polymer Aqueous Solutions

机译：单脉冲高能量电子辐照聚合物水溶液中自由基衰减动力学的数值模拟

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摘要

A new method for the numerical simulation of the radiation chemistry of aqueous polymer solutions is introduced. The method makes use of a deterministic approach combining the conventional homogeneous radiation chemistry of water with the chemistry of polymer radicals and other macromolecular species. The method is applied on single-pulse irradiations of aqueous polymer solutions. The speciation of macromolecular species accounts for the variations in the number of alkyl radicals per chain, molecular weight, and number of internal loops (as a consequence of an intramolecular radical-radical combination). In the simulations, the initial polymer molecular weight, polymer concentration, and dose per pulse (function of pulse length and dose rate during the pulse) were systematically varied. In total, 54 different conditions were simulated. The results are well in line with the available experimental data for similar systems. At a low polymer concentration and a high dose per pulse, the kinetics of radical decay is quite complex for the competition between intra- and intermolecular radical-radical reactions, whereas at a low dose per pulse the kinetics is purely second-order. The simulations demonstrate the limitations of the polymer in scavenging all the radicals generated by water radiolysis when irradiated at a low polymer concentration and a high dose per pulse. They also show that the radical decay of lower-molecular-weight chains is faster and to a larger extent dominated by intermolecular radical-radical reactions, thus explaining the mechanism behind the experimentally observed narrowing of molecular weight distributions.
机译：介绍了一种新的辐射化学物质模拟方法的含水聚合物溶液的数值模拟。该方法利用常规均匀辐射化学水与聚合物自由基和其他大分子物种的化学方法的确定性方法。该方法应用于单脉冲水溶液溶液的单脉冲照射。大分子物种的形态占烷基的数量的变化，烷基自由基的每种链条，分子量和内部环的数量（作为分子内自由基组合的结果）。在模拟中，系统地改变了初始聚合物分子量，聚合物浓度，聚合物浓度和每脉冲的剂量（脉冲长度和剂量率的函数）。总共模拟了54种不同的条件。结果与类似系统的可用实验数据一致。在低聚合物浓度和每次脉冲的高剂量时，激进衰减的动力学对于血液分子和分子间自由基反应之间的竞争非常复杂，而在每次脉冲低剂量时，动力学纯度是二阶。该模拟证明了聚合物在清除水辐射产生的所有基团时的局限性，当以低聚合物浓度和每脉冲的高剂量照射时。他们还表明，较低分子量链的根本衰减速度更快，并且在更大程度上以分子间自由基反应为主，因此解释了实验观察到的分子量分布缩小后的机制。

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