Department of Engineering Science and Mechanics, Virginia Tech, Blacksburg, Virginia 24061, USA.
J Chem Phys. 2012 Jan 28;136(4):044901. doi: 10.1063/1.3678848.
If their thermal conductivity can be lowered, polyacetylene (PA) and polyaniline (PANI) offer examples of electrically conducting polymers that can have potential use as thermoelectrics. Thermal transport in such polymers is primarily influenced by bonded interactions and chain orientations relative to the direction of heat transfer. We employ molecular dynamics simulations to investigate two mechanisms to control the phonon thermal transport in PANI and PA, namely, (1) mechanical strain and (2) polymer combinations. The molecular configurations of PA and PANI have a significant influence on their thermal transport characteristics. The axial thermal conductivity increases when a polymer is axially stretched but decreases under transverse tension. Since the strain dependence of the thermal conductivity is related to the phonon scattering among neighboring polymer chains, this behavior is examined through Herman's orientation factor that quantifies the degree of chain alignment in a given direction. The conductivity is enhanced as adjacent chains become more aligned along the direction of heat conduction but diminishes when they are orthogonally oriented to it. Physically combining these polymers reduces the thermal conductivity, which reaches a minimum value for a 2:3 PANI/PA chain ratio.
如果它们的导热系数能够降低，聚乙炔（PA）和聚苯胺（PANI）就是具有潜在热电应用的导电聚合物的例子。这种聚合物中的热传递主要受键合相互作用和链相对于热传递方向的取向的影响。我们采用分子动力学模拟来研究控制聚苯胺和聚乙炔中声子热输运的两种机制，即（1）机械应变和（2）聚合物组合。PA 和 PANI 的分子结构对它们的热传输特性有很大的影响。聚合物轴向拉伸时轴向热导率增加，但横向拉伸时则减小。由于热导率的应变依赖性与相邻聚合物链之间的声子散射有关，因此通过赫尔曼取向因子来研究这种行为，该因子量化了给定方向上链对齐的程度。当相邻链沿热传导方向更加对齐时，电导率会增强，但当它们垂直于该方向时，电导率会减弱。物理上结合这些聚合物会降低热导率，当 PANI/PA 链比为 2:3 时，热导率达到最小值。
