Thermal conductance of Teflon and Polyethylene: Insight from an atomistic, single-molecule level

Abstract

The thermal transport properties of teflon (polytetrafluoroethylene) and its polyethylene counterparts are, while highly desirable and widely used, only superficially understood. Here, we aim therefore to provide rigorous insight from an atomistic point of view in context of single-molecule devices. We show that for vinyl polymers adsorbed on metal-surfaces the thermal transport strongly depends on the properties of the metal-molecule interface and that the reduced thermal conductance observed for teflon derivatives originates in a reduced phonon injection life time. In asymmetric molecules phonon blocking on the intra molecular interface leads to a further reduction of thermal conductance. For hetrojunctions with different electrode materials we find that thermal conductance is suppressed due to a reduced overlap of the available phonon modes in the different electrodes. A detailed atomistic picture is thereby provided by studying the transport through perfluorooctane and octane on a single-molecule level using first principles transport calculations and nonequilibrium molecular dynamic simulations.

Revealing Factors Influencing the Fluorine‐Centered Non‐Covalent Interactions in Some Fluorine‐Substituted Molecular Complexes: Insights from First‐Principles Studies

“…This active halogen has found application not only in organic synthesis, but has also created its own place in medicinal chemistry and drug design, as well as in organic electronics ,. It plays a vital role in the development of a variety of sophisticated and widely used materials, with Teflon, polytetrafluoroethylene (PTFE), probably most widely known …”

“…[6,7] It plays a vital role in the development of a variety of sophisticated and widely used materials, [6][7][8] with Teflon, polytetrafluoroethylene (PTFE), probably most widely known. [9] Fluorine displays low polarizing affinity compared to the heavier halogens Cl, Br and I, and this probably explains its low tendency to participate in halogen bonding. [10][11][12][13][14][15][16][17][18][19][20] Because the three heavier halogens are easily polarizable in molecules, they are usually accompanied by regions of positive electrostatic potential along the outermost extension of the RÀX (X=Cl, Br, I) covalent bond in many molecules, where R is the remainder part of the molecule.…”

Transmission eigenchannels for coherent phonon transport

“…In this situation, the phonon transport is described within the framework of the Landauer-Büttiker scattering theory in which the contribution to the thermal conductance is determined by the elastic phonon transmission function of the system [8,9]. Different strategies have been put forward to compute this transmission function based on, for instance, the scattering matrix approach [10][11][12][13][14], mode matching theory [15][16][17], or nonequilibrium Green's function (NEGF) techniques [18][19][20][21][22][23][24][25][26][27]. These approaches are nicely summarized in Ref.…”

Определение Частотной Зависимости Комплексной Теплопроводности Тонких Полимерных Пленок

“…Считая нижнюю границу теплоизолированной, приходим к условию 0.28 ± 0.02 0.25 [10], 0.272 [11], 0.275 [12] Подставляя равенства (16)−(19) в уравнения (7), (8), получим…”

“…В справочных данных [8][9][10][11][12] приводятся значения статических теплопроводностей λ S , соответствующих неравенству (3) или, что то же самое, условию ω = 0, т. е. λ S = lim ω→0 λ ′ (ω).…”