Chain conformation-dependent thermal conductivity of amorphous polymer blends: the impact of inter- and intra-chain interactions

Wei, Xingfei; Zhang, Teng; Luo, Tengfei

doi:10.1039/c6cp06643g

Cited by 71 publications

(100 citation statements)

References 40 publications

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“…This high thermal conductivity is attributed to the H-bond networks formed by these three polymer blends (PVA, lignin and gelatin) to supply more heat transfer pathways, as illustrated in Fig In addition to bridging different polymer chains to form heat-transfer networks (bridging effect), H-bonds could also serve as "soft grips" to suppress the segmental rotation of polymers, which reduces phonon scattering and thus leading to a higher thermal conductivity [53,54]. Through MD simulations of amorphous polymer blends, Wei et al [55] proposed that locally ordered lamellar structures could form in the polymer blends due to the large inter-chain interactions and thus enhancing the thermal conductivity.…”

Section: Fig 13 Thermal Conductivity Of Polymer Blends By Engineerinmentioning

confidence: 99%

Thermal conductivity of polymers and polymer nanocomposites

Huang

Qian

Yang

2018

Materials Science and Engineering: R: Reports

633

391

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Polymers are widely used in industry and in our daily life because of their diverse functionality, light weight, low cost and excellent chemical stability. However, on some applications such as heat exchangers and electronic packaging, the low thermal conductivity of polymers is one of the major technological barriers. Enhancing the thermal conductivity of polymers is important for these applications and has become a very active research topic over the past two decades. In this review article, we aim to: 1). systematically summarize the molecular level understanding on the thermal transport mechanisms in polymers in terms of polymer morphology, chain structure and inter-chain coupling; 2). highlight the rationales in the recent efforts in enhancing the thermal conductivity of nanostructured polymers and polymer nanocomposites. Finally, we outline the main advances, challenges and outlooks for highly thermal-conductive polymer and polymer nanocomposites. the inter-chain coupling. Fig. 1 Schematic diagrams of a polymer: (a) the morphology of a polymer consisting of crystalline and amorphous domains; (b) structure of a polymer chain.In addition to engineering the morphology of polymer chains, another common method to enhance the thermal conductivity of polymers is to blend polymers with highly thermal conductive fillers. The progress of nanotechnology over the last two decades not only provides more diverse high thermal conductivity fillers of different material types and topological shapes but also advances the understanding at the nanoscale. Fig. 2 shows a sketch of a polymer nanocomposite to illustrate the thermal transport mechanisms. In general, there are two types of polymer nanocomposites depending on whether nano-fillers form a network or not. When the filler concentration is low, no inter-filler networks could be formed, as shown in Fig. 2(a). The thermal conductivity is essentially determined by the filler-matrix coupling, i.e, interfacial thermal resistance, and the concentration and the geometric shapes of fillers. When the filler concentration is large enough, high conductivity fillers might form thermally conductive networks, as shown in Fig. 2(b). Although nanocomposites with filler network could possess a higher thermal conductivity than that without a network, their thermal conductivity could still be low due to the large inter-filler thermal contact resistance. Recently, three-dimensional fillers, such as carbon and graphene foams, have drawn a lot of attention. The fundamental thermal transport mechanisms and recent synthesis efforts in both types of nanocomposites are reviewed.This review article is organized as follows. In Section 2, we introduce the experimental progress on the enhancement of thermal conductivity by aligning polymer chains, and then review the methods to further tune the thermal conductivity by engineering chain structure and inter-chain coupling, as illustrated in Fig. 3(a). In Section 3, we discuss the thermal conductivity of polymer nanocomposites both with and without inter...

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Section: Fig 13 Thermal Conductivity Of Polymer Blends By Engineerinmentioning

confidence: 99%

Thermal conductivity of polymers and polymer nanocomposites

Huang

Qian

Yang

2018

Materials Science and Engineering: R: Reports

633

391

View full text Add to dashboard Cite

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“…This is because thermal transport in amorphous polymer is dominated by the covalent bonds along the chain backbones and when such backbones are extended, thermal conductivity increases. 14,15 In bulk condensed polyelectrolytes, where the counterion concentration is high and the interchain interaction is strong, the counterion condensation theory suggests that the polymer chain will collapse. [16][17][18] Thus, the observed thermal conductivity increase (in Fig.…”

Section: The Molecular Conformation Has No Effect On Thermal Conductimentioning

confidence: 99%

Role of Ionization in Thermal Transport of Solid Polyelectrolytes

Wei

Luo

2019

J. Phys. Chem. C

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Amorphous polymers are known as thermal insulators, increasing their thermal conductivities have not been guided by fully understood physics. In this work, we use molecular dynamics simulations to study the thermal transport mechanism of solid polyelectrolytes, poly(acrylic acid) (PAA) and its ionized forms. The thermal conductivity of PAA increases monotonically with the ionization strength. Although stronger ionization induces larger Coulombic interactions, the Coulombic interaction does not directly contribute to the thermal conductivity enhancement.Instead, it enhances thermal transport through the Lennard-Jones (LJ) interaction. The strong Coulombic force between the counterion and the ionized carboxylic group shifts the LJ force to the stronger LJ repulsive regime, which is mainly responsible for the improved thermal conductivity. Applying a high pressure can further reduce the inter-atomic distance and trigger the thermal transport through the LJ interaction. A thermal conductivity of 1.09 W/m.K can be achieved at 11.2 GPa in an ionized PAA.

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“…4,5 In polymers, along the molecular backbone direction heat transfer can be very efficient due to the strong covalent bonds, while in the interchain direction heat transfer is much less efficient due to the weak non-bonding interactions. [6][7][8][9] A number of recent studies have revealed that polymer thermal conductivity is strongly related to its molecular level conformation. 6,8,[10][11][12][13][14] For example, stiffer molecular backbones can make the chains straighter even in the amorphous state 15 and thus increase the amount of heat that can be transferred through the strong backbone.…”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity of Polyelectrolytes with Different Counterions

Wei

Luo

2020

J. Phys. Chem. C

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Polyelectrolytes are important to many applications, such as electronics and batteries. In this work, we study the thermal conductivity of polyelectrolytes with different counterions using molecular dynamics (MD) simulations. Both anionic and cationic polyelectrolytes, including poly(acrylic acid) and poly(allylamine hydrogen halide), are investigated. We have simulated a total number of 17 polyelectrolytes with different counterions and we find that all of them have thermal conductivity values between 0.2 and 0.7 W/(m.K). By analyzing thermal conductivity against different counterion descriptors (atomic mass, atomic radius, van der Waals radius and ionic radius), we find a strong negative relationship between thermal conductivity and the ionic radii of counterions. We rationalize such a discovery through analyzing the heat flux at molecular level and find that thermal conductivity shows a general increasing trend with respect to the interatomic non-bonding forces and atomic velocities. We have also found a positive correlation between the MD-calculated thermal conductivity and that from the minimum thermal conductivity model, and this correlation can also be traced back to the same molecular level origin. Our study provides new insights to the heat transfer physics in polymers and may help scientists develop polyelectrolytes with desirable thermal conductivity.

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Chain conformation-dependent thermal conductivity of amorphous polymer blends: the impact of inter- and intra-chain interactions

Cited by 71 publications

References 40 publications

Thermal conductivity of polymers and polymer nanocomposites

Thermal conductivity of polymers and polymer nanocomposites

Role of Ionization in Thermal Transport of Solid Polyelectrolytes

Thermal Conductivity of Polyelectrolytes with Different Counterions

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