Polymer Nanofibers with Outstanding Thermal Conductivity and Thermal Stability: Fundamental Linkage between Molecular Characteristics and Macroscopic Thermal Properties
Polymer Nanofibers with Outstanding Thermal Conductivity and Thermal Stability: Fundamental Linkage between Molecular Characteristics and Macroscopic Thermal Properties
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DOI：
10.1021/jp5051639
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
Teng Zhang;Xufei Wu;T. Luo
中科院分区：
文献类型：
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作者：
Teng Zhang;Xufei Wu;T. Luo
聚合物纳米纤维具有高导热系数和优异的热稳定性，在热管理、换热器和储能等传热关键应用中具有非常重要的应用价值。在这项工作中，我们通过研究一系列聚合物纳米纤维的温度诱导相变和热输运，揭示了聚合物纳米纤维的热导率和热稳定性与其分子特性之间的基本关系。采用大尺度分子动力学模拟方法，对10种不同分子结构的聚合物纳米纤维进行了研究。我们发现，在具有刚性骨架的聚合物中，由于链段旋转和大的声子群速度被抑制，{\pi}共轭聚合物可以获得高的导热系数和良好的热稳定性。节段旋转的低几率不仅阻止了温度诱导的相变，而且由于减少了无序散射，使得声子平均自由程变长。虽然更强的链间相互作用也可以提高热稳定性，但具有这种特征的聚合物通常具有较重的原子、较弱的主干键和易受随机旋转的链段，这导致热导率较低。这项工作阐明了聚合物纳米纤维的分子性质与宏观热性能之间的内在联系，这对于设计具有高温稳定性的导热聚合物纳米纤维具有重要意义。
Polymer nanofibers with high thermal conductivities and outstanding thermal stabilities are highly desirable in heat transfer-critical applications such as thermal management, heat exchangers and energy storage. In this work, we unlock the fundamental relations between the thermal conductivity and thermal stability of polymer nanofibers and their molecular characteristics by studying the temperature-induced phase transitions and thermal transport of a series of polymer nanofibers. Ten different polymer nanofibers with systematically chosen molecular structures are studied using large scale molecular dynamics simulations. We found that high thermal conductivity and good thermal stability can be achieved in polymers with rigid backbones, exemplified by {\pi}-conjugated polymers, due to suppressed segmental rotations and large phonon group velocities. The low probability of segmental rotation does not only prevent temperature-induced phase transition but also enables long phonon mean free paths due to reduced disorder scattering. Although stronger inter-chain interactions can also improve the thermal stability, polymers with such a feature usually have heavier atoms, weaker backbone bonds, and segments vulnerable to random rotations, which lead to low thermal conductivities. This work elucidates the underlying linkage between the molecular nature and macroscopic thermal properties of polymer nanofibers, which is instrumental to the design of thermally conductive polymer nanofibers with high temperature stabilities.