Ab Initio Quantitative Prediction of Tacticity in Radical Polymerization of Poly(methyl methacrylate) by a Molecular Simulation Technique with the Conformation Indexing for Multiple Transition States,The Journal of Physical Chemistry C

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Ab Initio Quantitative Prediction of Tacticity in Radical Polymerization of Poly(methyl methacrylate) by a Molecular Simulation Technique with the Conformation Indexing for Multiple Transition States
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-07-10 , DOI: 10.1021/acs.jpcc.0c01812
Zizhen Rao ₁ , Masayoshi Takayanagi _{2,

3,

4} , Masataka Nagaoka _{1,

2,

5}

Affiliation

Free-radical polymerization is a critical route for generating vinyl polymers owing to its versatility and productivity, while the realization of stereospecific propagation has been considered very difficult and demanding. Therefore, a concrete investigation on the mechanism of tacticity obtained in radical polymerization is urgent. Experimentally, tacticity of poly(methyl methacrylate) produced by radical polymerization in bulk was reported to be syndiotactic and temperature-dependent. In this study, we intended to rationalize those behaviors on the microscopic scale via density functional theory calculations and a hybrid Monte Carlo/molecular dynamics simulation [Red Moon methodology]. We devised a unique conformation indexing based on the multidimensional conformational analysis and obtained as many as 576 transition state conformations for the propagation reaction. Boltzmann factors of the 576 conformations implied the overall higher stability of pro-racemo conformations than pro-meso ones and, in addition, the more syndiotactic tendency at low temperature. By the Red Moon simulations utilizing the energy barriers of those conformations, we successfully simulated the propagation reaction process and achieved quantitative agreement of the product tacticity. These results exhibit the validity of our ab initio molecular simulation procedure with the conformation indexing to realize quantitative analysis of the selectivity of reactions.

中文翻译：

分子模拟技术从头开始定量预测聚甲基丙烯酸甲酯的自由基聚合反应的立构规整度

由于自由基聚合反应的多功能性和生产率，它是生产乙烯基聚合物的关键途径，而立体定向繁殖的实现被认为是非常困难和苛刻的。因此，迫切需要对在自由基聚合中获得的立构规整机理进行具体研究。在实验上，据报道通过自由基聚合本体生产的聚（甲基丙烯酸甲酯）的立构规整度是间同立构的并且是温度依赖性的。在这项研究中，我们打算通过密度泛函理论计算和混合蒙特卡洛/分子动力学模拟[Red Moon方法]在微观尺度上合理化这些行为。我们基于多维构象分析设计了独特的构象索引，并为传播反应获得了多达576种过渡态构象。576个构象的玻尔兹曼因子暗示了前消旋构象的整体稳定性高于中消旋构象的稳定性，此外，在低温下更趋于间同。通过利用这些构象的能垒进行的Red Moon仿真，我们成功地模拟了传播反应过程，并获得了产物立构规整度的定量协议。这些结果证明了我们的从头算分子模拟程序的正确性，并利用构象索引实现了反应选择性的定量分析。576个构象的玻尔兹曼因子暗示了前消旋构象的整体稳定性高于中消旋构象的稳定性，此外，在低温下更趋于间同。通过利用这些构象的能垒进行的红月模拟，我们成功地模拟了传播反应过程，并获得了产物立构规整度的定量协议。这些结果证明了我们的从头算分子模拟程序的正确性，其构象索引可实现对反应选择性的定量分析。576个构象的玻尔兹曼因子暗示了前消旋构象的整体稳定性高于中消旋构象的稳定性，此外，在低温下更趋于间同。通过利用这些构象的能垒进行的红月模拟，我们成功地模拟了传播反应过程，并获得了产物立构规整度的定量协议。这些结果证明了我们的从头算分子模拟程序的正确性，其构象索引可实现对反应选择性的定量分析。我们成功地模拟了增殖反应过程，并获得了产物立构规整度的定量协议。这些结果证明了我们的从头算分子模拟程序的正确性，其构象索引可实现对反应选择性的定量分析。我们成功地模拟了增殖反应过程，并获得了产物立构规整度的定量协议。这些结果证明了我们的从头算分子模拟程序的正确性，其构象索引可实现对反应选择性的定量分析。

更新日期：2020-08-06

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