Li Pengfei, Yang Sui, Zhang Teng, Shrestha Ramesh, Hippalgaonkar Kedar, Luo Tengfei, Zhang Xiang, Shen Sheng
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, 15213, United States.
Department of Mechanical Engineering, University of California, Berkeley, 94720, United States.
Sci Rep. 2016 Feb 22;6:21452. doi: 10.1038/srep21452.
Crystalline polymers have attracted significant interest in recent years due to their enhanced mechanical and thermal properties. As one type of organic-inorganic hybrid polymer crystals, polysilsesquioxane can be synthesized by large-scale and inexpensive so-gel processes with two precursors. In this paper, both octylene-bridged and hexylene-bridged PSQ crystals are characterized with infrared spectroscopy and X-ray crystallography to reveal their super high crystallinity. To study the thermal transport in these unique polymer crystals, we use a suspended micro thermal device to examine their thermal properties from 20 K to 320 K, and demonstrate their tunable thermal conductivity by varying the length of alkyl chains. We also conduct non-equilibrium molecular dynamics simulations to study the phonon behaviors across the hydrogen bond interface. The simulation results demonstrate good agreement with the experimental results regarding both the value and trend of the PSQ thermal conductivity. Furthermore, from the simulation, we find that the anharmonic phonon scattering and interfacial anharmnic coupling effects across the hydrogen bond interface may explain the experimentally observed thermal properties.
近年来，结晶聚合物因其增强的机械性能和热性能而备受关注。作为一种有机-无机杂化聚合物晶体，聚倍半硅氧烷可以通过大规模且廉价的溶胶-凝胶法由两种前驱体合成。在本文中，通过红外光谱和X射线晶体学对辛烯桥联和己烯桥联的聚倍半硅氧烷晶体进行了表征，以揭示它们的超高结晶度。为了研究这些独特聚合物晶体中的热输运，我们使用悬浮微热装置从20 K到320 K检测它们的热性能，并通过改变烷基链的长度来证明它们可调的热导率。我们还进行了非平衡分子动力学模拟，以研究氢键界面处的声子行为。模拟结果在聚倍半硅氧烷热导率的值和趋势方面与实验结果显示出良好的一致性。此外，从模拟中我们发现，氢键界面处的非谐声子散射和界面非谐耦合效应可能解释了实验观察到的热性能。
