Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study
Yoshiaki Kawagoe1, Donatas Surblys2, Hiroki Matsubara2
1Department of Aerospace Engineering, Tohoku University, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 26, 2020
Summary
This study explores heat conduction in layer-by-layer (LbL) membranes, finding that controlling molecular orientation and charge density enhances thermal conductivity in both cross-plane and in-plane directions.
Area of Science:
- Materials Science
- Nanotechnology
- Computational Physics
Background:
- Anisotropic heat conduction in materials is crucial for controlling heat flow at the nanoscale.
- Layer-by-layer (LbL) membranes, formed by electrostatic assembly of polyelectrolytes, offer tunable thermal properties.
- Understanding heat transport in LbL membranes requires molecular-level simulations.
Purpose of the Study:
- To investigate the anisotropic heat conduction characteristics of poly(acrylic acid)/polyethylenimine (PAA/PEI) LbL membranes.
- To determine the influence of the degree of ionization on thermal boundary resistance and conductivity.
- To elucidate the mechanisms behind enhanced heat conduction in both cross-plane and in-plane directions.
Main Methods:
- Molecular dynamics simulations were employed to model PAA/PEI LbL membranes sandwiched between charged solid walls.
- Thermal boundary resistance and thermal conductivity were calculated for cross-plane and in-plane directions.
- The effect of varying degrees of ionization (surface charge density and molecular charge) was systematically studied.
Main Results:
- Thermal boundary resistance in the cross-plane direction decreases with increasing degree of ionization.
- Cross-plane thermal conductivity of constituent layers is influenced by molecular orientation, initially increasing then decreasing with ionization.
- In-plane thermal conductivity is enhanced due to the alignment of polymer chains in the in-plane direction.
Conclusions:
- The study demonstrates that LbL membranes exhibit anisotropic heat conduction.
- Electrostatic interactions and molecular alignment significantly enhance three-dimensional heat conduction compared to bulk polymers.
- Tuning the degree of ionization offers a pathway to control heat flow in nanoscale devices.
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