Session: 11-60-01: Simulations of Thermal Transport in Nanostructures and across Interfaces

Paper Number: 120141

120141 - Improvement of Thermal Transport Across Graphene/polymer Interfaces With Hydrogen Bond and Polymer Brush 

The thermal performance of many materials systems depends on interface thermal transport properties. For thermal management purposes, graphene-polymer systems are prime candidates. However, due to the low thermal conductivity of pure bulk polymers, their application has been limited. As a result, numerous filler materials (e.g. graphene, carbon nanotubes, solid particles, etc.) have been proposed to increase the effective thermal conductivity. Recently, self-assembled monolayers and polymer brushes have been proven to reach unprecedented interfacial effective properties, thus making the use of polymers more viable. However, despite the enhancements, the thermal conductivities of polymer interface materials are still far below theoretical predictions, mainly due to the inefficient thermal transport across material interfaces. The lower thermal conductivity at the interface is due to abrupt changes in temperature and poor phonon coupling. This complicated nature of thermal transport in graphene–polymer systems and the transport process has been poorly understood. In this work, graphene-grafted polymers (PVA, PE) in a polymer matrix (PMMA) have been studied with the help of molecular dynamics, length effect on interface thermal conductance shows higher chain length reaches higher thermal conductivity at the interface. The thermal conductivity at the interface is enhanced by hierarchically arranged hydrogen bonds and better phonon coupling. And due to the grafted chains, the temperature change across the interface is gradual and smoother. The thermal transport enhancement is tunable by varying the number of grafted chains and the density of hydrogen bonds in the unique hierarchical hydrogen bond network. The two types of hydrogen bonds, i.e. PVA–PMMA hydrogen bonds and PVA–PVA hydrogen bonds, are analyzed and their effects on various structural and thermal properties are systematically investigated. As the chain length increases, several hydrogen bonds both within PVA-PVA and PVA-PMMA increase which results in higher thermal conductivity. The chain orientation reveals that a straight stand-up position is more favorable for better thermal transport. This study also investigates polymer brushes as the grafting polymer at the graphene-polymer interface. Further, polymer brush orientation and side-chain effect on effective transport properties have been investigated. This study finds that taper bottle brush-shaped polymer has higher effectiveness as grafted polymers than traditional brush polymers. The taper portion of the brush polymers has better directional transport properties due to being more stable and having less presence of randomness. And the larger side chains have better phonon coupling and can achieve better thermal transport properties. These results are expected to provide new physical insights for interface engineering to achieve tunable thermal management and energy efficiency in a wide variety of systems.

Presenting Author: MD MOHAIMINUL ISLAM Temple University

Presenting Author Biography: Md Mohaiminul Islam is currently a Ph.D. student at Temple University in the Department of Mechanical Engineering. His research interest lies in computational mechanics, computational materials, and machine learning. He is currently the Loretta C Duckworth Studio fellow at Tempe University Library. His current endeavors involve Phase-field modeling, Topology optimization, and data-driven approaches to engineering problems.

Authors:

MD MOHAIMINUL ISLAM Temple University
Ling Liu Temple University