title: Tunable Thermal Transport in Polysilsesquioxane (PSQ) Hybrid Crystals.
abstract: 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.
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, 15213, United States.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Mechanical Engineering, University of California, Berkeley, 94720, United States.
authors.forename: Sui
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, 46556, United States.
authors.forename: Teng
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, 15213, United States.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Shrestha
authors.affiliation: Institute of Materials Research and Engineering, Singapore 117602, Singapore.
authors.forename: Kedar
authors.initials: K
authors.lastname: Hippalgaonkar
authors.affiliation: Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, 46556, United States.
authors.forename: Tengfei
authors.initials: T
authors.lastname: Luo
authors.affiliation: Department of Mechanical Engineering, University of California, Berkeley, 94720, United States.|Department of Physics, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, 15213, United States.
authors.forename: Sheng
authors.initials: S
authors.lastname: Shen