Quantitative Theoretical Study of Molecular and Chain-Level Conformational Properties of Poly(ferrocenyldimethylsilanes)
Quantitative Theoretical Study of Molecular and Chain-Level Conformational Properties of Poly(ferrocenyldimethylsilanes)
复制标题
聚二茂铁基二甲基硅烷分子和链级构象性质的定量理论研究
DOI：
10.1021/acs.macromol.1c01865
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发表时间：
2021
期刊：
影响因子：
5.5
通讯作者：
Rui Zhang
中科院分区：
文献类型：
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作者：
Y. Han;Rui Zhang
聚二茂铁硅烷（pfs）是一类重要的含过渡金属聚合物。在这项工作中，我们报告了最具代表性的PFS聚合物：聚二茂铁基二甲基硅烷（PFDMS）的分子和链级构象性质的系统理论研究。利用密度泛函理论（DFT）寻找二聚体和三聚体PFDMS低聚物的局部最小能态的完备集。为这些低能构象确定的几何和能量参数为构建具有任何聚合程度的无扰动PFDMS链的新型旋转异构态（RIS）模型提供了准确的输入信息。为了在标准RIS理论框架中正确处理二铁单元的特殊分子结构，最初提出了一个适用于整个PFS类的“有效骨架”概念。由此产生的RIS理论用于研究无扰动PFDMS的广泛构象统计力学性能（端到端距离的均方，旋转半径的均方，温度系数等）。首次定量预测了PFDMS的特征比和库恩长度（当ent = 25°C时，C∞= 8.4,lk = 1.9 nm）。本文开发的DFT-RIS组合方法可以很容易地扩展到研究其他类型的PFS聚合物的单链性质。这种通用性可能会促使未来在更广泛的PFS聚合物上产生一些有趣的新的DFT和RIS计算。
Polyferrocenylsilanes (PFSs) represent an important class of transition metal-containing polymers. In this work, we report a systematical theoretical study of molecular and chain-level conformational properties of the most representative PFS polymer: poly(ferrocenyldimethylsilane) (PFDMS). The density functional theory (DFT) is employed to search out the complete set of local minimum energy states of dimeric and trimeric PFDMS oligomers. The geometrical and energetic parameters determined for these low-energy conformations provide accurate input information to construct a novel rotational isomeric state (RIS) model for an unperturbed PFDMS chain with any degree of polymerization. To properly treat the special molecular structure of ferrocene units in the standard RIS theoretical framework, an “effective backbone” concept that is generic for the whole PFS class is originally proposed. The resulting RIS theory is used to investigate a wide range of conformational statistical mechanical properties (mean square end-to-end distance, mean square radius of gyration, temperature coefficient, etc.) of an unperturbed PFDMS. The previously unknown characteristic ratio and Kuhn length of PFDMS are quantitatively predicted for the first time (C∞= 8.4 andlK= 1.9 nm whenT= 25 °C). The DFT-RIS combinatory approach developed herein can be readily extended to study single-chain properties of other types of PFS polymers. This generality might urge some interesting new DFT and RIS calculations on a broader range of PFS polymers in the future.