Thermal resistance network model for heat conduction of amorphous polymers

Abstract

Thermal conductivities (TCs) of the vast majority of amorphous polymers are in a very narrow range, 0.1 ∼ 0.5 Wm −1 K −1 , although single polymer chains possess TC of orders-of-magnitude higher. Entanglement of polymer chains plays an important role in determining the TC of bulk polymers. We propose a thermal resistance network (TRN) model for TC in amorphous polymers taking into account the entanglement of molecular chains. Our model explains well the physical origin of universally low TC observed in amorphous polymers. The empirical formulae of pressure and temperature dependence of TC can be successfully reproduced from our model not only in solid polymers but also in polymer melts. We further quantitatively explain the anisotropic TC in oriented polymers.

Thermal Conductivity of Polyelectrolytes with Different Counterions

“…It is natural to believe that smaller ionic radii would result in shorter interaction distances between the counterion and the ionized groups on polymers; as a result, these distances should also show similar correlation with thermal conductivity as the ionic radii. 42 We then calculate the radial distribution function (RDF) of the ionized oxygen atoms of the polymer around the cations and the ionized nitrogen atoms around the anions (see Section S4 in the Supporting Information). The position of the first peak in such RDF profiles (listed in Table S5 in the Supporting Information) should be correlated to the ionic radii, 19,43,44 and thus, we use the first peak position as another feature.…”

“…The ionic radius describes the effective size of the counterion due to interatomic interactions with other atoms, which includes vdW and Coulombic forces. It is natural to believe that smaller ionic radii would result in shorter interaction distances between the counterion and the ionized groups on polymers; as a result, these distances should also show similar correlation with thermal conductivity as the ionic radii . We then calculate the radial distribution function (RDF) of the ionized oxygen atoms of the polymer around the cations and the ionized nitrogen atoms around the anions (see Section S4 in the Supporting Information).…”

High Thermal Conductivity in Anisotropic Aligned Polymeric Materials

“…The different β and TC of polymer chains give indications of the effects on thermal transport of bond strength/mass disorder and interaction between molecules (Figure c) . Additionally, it found that there is an interchain distance-dependent TC in isotropic polymers, revealing the mechanism of different TC in various polymers and the positive effect of entanglement . However, the interchain distance-dependent TC is negligible in oriented polymers because the TC of oriented polymers is dominated by the intrinsic TC of molecular chains .…”

Thermal conductivity of amorphous polymers and its dependence on molecular weight

“…These simulation results show good qualitative agreement with a recent model proposed by Xi et al [22] with a general expression for the thermal conductivity of amorphous materials ranging from liquids to polymer glasses (i.e., for amorphous solids λ is found to be dependent on M and for polymer glasses it is found to be independent). To describe the thermal conductivity of polymers, this model makes use of a Thermal Resistance Network that highlights the importance of the distance between entanglements in the path followed by energy carriers along the chains [22,23]. This model has successfully reproduced the pressure and temperature dependence of λ in polymer solids and melts and qualitatively described anisotropy in oriented polymers.…”