Muthaiah Rajmohan, Tarannum Fatema, Danayat Swapneel, Annam Roshan Sameer, Nayal Avinash Singh, Yedukondalu N, Garg Jivtesh
School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, 73019, USA.
Department of Geosciences, Stony Brook University, Stony Brook, New York 11794-2100, USA.
Phys Chem Chem Phys. 2022 Jun 15;24(23):14640-14650. doi: 10.1039/d2cp00146b.
To achieve polymer-graphene nanocomposites with high thermal conductivity (), it is critically important to achieve efficient thermal coupling between graphene and the surrounding polymer matrix through effective functionalization schemes. In this work, we demonstrate that edge-functionalization of graphene nanoplatelets (GnPs) can enable a larger enhancement of effective thermal conductivity in polymer-graphene nanocomposites relative to basal plane functionalization. Effective thermal conductivity for the edge case is predicted, through molecular dynamics simulations, to be up to 48% higher relative to basal plane bonding for 35 wt% graphene loading with 10 layer thick nanoplatelets. The beneficial effect of edge bonding is related to the anisotropy of thermal transport in graphene, involving very high in-plane thermal conductivity (∼2000 W m K) compared to the low out-of-plane thermal conductivity (∼10 W m K). Likewise, in multilayer graphene nanoplatelets (GnPs), the thermal conductivity across the layers is even lower due to the weak van der Waals bonding between each pair of layers. Edge functionalization couples the polymer chains to the high in-plane thermal conduction pathway of graphene, thus leading to overall high thermal conductivity of the composite. Basal-plane functionalization, however, lowers the thermal resistance between the polymer and the surface graphene sheets of the nanoplatelet only, causing the heat conduction through inner layers to be less efficient, thus resulting in the basal plane scheme to be outperformed by the edge scheme. The present study enables fundamentally novel pathways for achieving high thermal conductivity polymer nanocomposites.
为了实现具有高导热率（）的聚合物 - 石墨烯纳米复合材料，通过有效的功能化方案实现石墨烯与周围聚合物基体之间的高效热耦合至关重要。在这项工作中，我们证明相对于基面功能化，石墨烯纳米片（GnPs）的边缘功能化能够在聚合物 - 石墨烯纳米复合材料中实现更大程度的有效导热率增强。通过分子动力学模拟预测，对于35 wt%石墨烯负载且纳米片厚度为10层的情况，边缘功能化情况下的有效导热率相对于基面键合可高达48%。边缘键合的有益效果与石墨烯中热传输的各向异性有关，其面内热导率非常高（约2000 W m K），而面外热导率很低（约10 W m K）。同样，在多层石墨烯纳米片（GnPs）中，由于每对层之间的范德华键较弱，跨层的热导率甚至更低。边缘功能化将聚合物链与石墨烯的高面内热传导路径耦合，从而导致复合材料整体具有高导热率。然而，基面功能化仅降低了聚合物与纳米片表面石墨烯片之间的热阻，使得通过内层的热传导效率较低，因此导致基面方案的性能不如边缘方案。本研究为实现高导热率聚合物纳米复合材料开辟了全新的途径。
