Wei Xingfei, Luo Tengfei
Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
Phys Chem Chem Phys. 2022 May 4;24(17):10272-10279. doi: 10.1039/d2cp01325h.
The light switchable thermal conductivity displayed by some polymers makes them promising for applications like data storage, temperature regulation and light switchable devices. In this study, the mechanism of thermal conductivity switching in poly[6-(4-phenyldiazenyl phenoxy)hexyl metharylate] is studied using molecular dynamics (MD) simulations. The π-π stacking and amorphous polymer structures are specifically prepared through different simulation procedures, and the thermal conductivity of these structures is calculated. It is found that due to the π-π stacking structure, the thermal conductivity along the side-chain direction can change by 30-50% (from 0.34 to 0.51 W m K). Through heat flux decomposition, it is found that the thermal conductivity change is dominated by the contribution from bonding interactions. This is because π-π stacking, which enforces the conformation, extends the side-chains of azobenzene polymers, making thermal transport in the side-chain direction more efficient. Along the polymer main-chain direction, the thermal conductivity is not affected by the π-π stacking of the side chains. This mechanism may be generalized to other types of polymers with azobenzene side-chains, which will develop a class of photo-responsive polymers.
一些聚合物所展现出的光可切换热导率使其在数据存储、温度调节和光可切换器件等应用方面颇具潜力。在本研究中，利用分子动力学（MD）模拟研究了聚[6-(4-苯基重氮苯氧基)己基甲基丙烯酸酯]中热导率切换的机制。通过不同的模拟程序专门制备了π-π堆积和无定形聚合物结构，并计算了这些结构的热导率。研究发现，由于π-π堆积结构，沿侧链方向的热导率可变化30 - 50%（从0.34到0.51 W m K）。通过热流分解发现，热导率的变化主要由键合相互作用的贡献主导。这是因为π-π堆积使构象得以强化，扩展了偶氮苯聚合物的侧链，使得沿侧链方向的热传输更高效。沿聚合物主链方向，热导率不受侧链π-π堆积的影响。这种机制可能适用于其他类型带有偶氮苯侧链的聚合物，这将开发出一类光响应聚合物。
