Superdiffusive Thermal Transport in Polymer-Grafted Nanoparticle Melts

IF 8.1 1区 物理与天体物理 Q1 PHYSICS, MULTIDISCIPLINARY
Bohai Liu, Mayank Jhalaria, Eric Ruzicka, Brian C. Benicewicz, Sanat K. Kumar, George Fytas, Xiangfan Xu
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引用次数: 0

Abstract

In contrast to normal diffusion processes, thermal conduction in one-dimensional systems is anomalous. The thermal conductivity is found to vary with the length as κ∼Lα(α>0), but there is a long-standing debate on the value α. Here, we present a canonical example of this behavior in polymer-grafted spherical nanoparticle (GNP) melts at fixed grafting density and nanoparticle radius. For long chains (chain length N945), the experimental κ(N) of GNP melts decreases with N, i.e., polymer concentration. For N<945, however, κ(N) unexpectedly increases with N with a maximum near N945. For these systems, the extensional free energy per polymer chain is predicted to be maximized near Nmax940 for σ≈0.47chains/nm2, which indicates the dominance of extended conformations at short N and Gaussian-like conformation for longer N. In the former regime, the thermal conductivity of extended polymer chains increases with N and follows κpNdry0.46±0.02, which provides experimental evidence of a novel class of superdiffusive thermal transport with α=1/2. Published by the American Physical Society 2024
聚合物接枝纳米颗粒熔体中的超扩散热输运
与正常扩散过程相反,一维系统中的热传导是反常的。热导率随长度变化为κ ~ Lα(α>0),但对α值存在长期争论。在这里,我们提出了在固定接枝密度和纳米颗粒半径下聚合物接枝球形纳米颗粒(GNP)熔体中这种行为的典型例子。对于长链(链长N≥945),GNP熔体的实验κ(N)随N(即聚合物浓度)的增加而减小。然而,对于N<;945, κ(N)意外地随N增加,并在N ~ 945附近达到最大值。对于这些体系,当σ≈0.47链/nm2时,每条聚合物链的拉伸自由能在Nmax≈940附近达到最大值,这表明在短N时,扩展构象占主导地位,而在长N时,类高斯构象占主导地位。在前者体系中,扩展聚合物链的热导率随着N的增加而增加,为κp ~ Ndry0.46±0.02,这为α=1/2的新型超扩散热输运提供了实验证据。2024年由美国物理学会出版
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来源期刊
Physical review letters
Physical review letters 物理-物理:综合
CiteScore
16.50
自引率
7.00%
发文量
2673
审稿时长
2.2 months
期刊介绍: Physical review letters(PRL)covers the full range of applied, fundamental, and interdisciplinary physics research topics: General physics, including statistical and quantum mechanics and quantum information Gravitation, astrophysics, and cosmology Elementary particles and fields Nuclear physics Atomic, molecular, and optical physics Nonlinear dynamics, fluid dynamics, and classical optics Plasma and beam physics Condensed matter and materials physics Polymers, soft matter, biological, climate and interdisciplinary physics, including networks
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