High thermal conductivity in amorphous polymer blends by engineered interchain interactions

Abstract

Thermal conductivity is an important property for polymers, as it often affects product reliability (for example, electronics packaging), functionality (for example, thermal interface materials) and/or manufacturing cost. However, polymer thermal conductivities primarily fall within a relatively narrow range (0.1-0.5 W m(-1) K(-1)) and are largely unexplored. Here, we show that a blend of two polymers with high miscibility and appropriately chosen linker structure can yield a dense and homogeneously distributed thermal network. A sharp increase in cross-plane thermal conductivity is observed under these conditions, reaching over 1.5 W m(-1) K(-1) in typical spin-cast polymer blend films of nanoscale thickness, which is approximately an order of magnitude larger than that of other amorphous polymers.

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…This approach is accompanied with introduction of large crystallinity [290,291] or hydrogen bonding [289,[292][293][294] in polymer blends.…”

High thermal conductivity in soft elastomers with elongated liquid metal inclusions

“…liquid metal | thermal conductivity | soft materials | soft robotics | stretchable electronics M aterials with high thermal conductivity are typically rigid and elastically incompatible with soft and mechanically deformable systems (1)(2)(3)(4)(5)(6). In the general case of nonmetallic and electrically insulating solids, this limitation arises from kinetic theory and the Newton−Laplace equation, which imply that thermal conductivity (k) will increase with a material's elastic modulus (E) according to the approximation k ≈ (E/ρ) 1/2 (C V ℓ/3), where C V is the volumetric heat capacity, ℓ is the average mean free path of phonons, and ρ is the density (7,8).…”

“…For polymers like polyethylene, thermal conductivity can be enhanced through macromolecular chain alignment (from k ≈ 0.3 W·m −1 ·K −1 to 100 W·m −1 ·K −1 ), but this also leads to a dramatic increase in elastic modulus from ∼1 GPa to 200 GPa (9). Likewise, glassy polymer blends have been engineered to increase thermal conductivity through interchain hydrogen bonding (1), and relatively higher thermal conductivity has been observed in amorphous polythiophene (k ≈ 4.4 W·m ) (2), but the high elastic modulus (E ≈ 3 GPa) and low strain at failure (<5% strain) of films make them unsuitable for soft functional materials (3).…”

Thermal conductivity enhancement of laser induced graphene foam upon P3HT infiltration

“…A high precision scale is used to measure the weight of 1 cm 2 sections of LIG on PI, and a scanning electron microscope is used to measure the thickness of each respective layer. These measured values and the manufacturer specified density of the PI film (1.42 g/cm 3 ) are then used to calculate the LIG density. Using the measured 6% duty cycle LIG density and the measured bulk thermal conductivity as a function of polymer filling (k Bulk ), the estimated ligament thermal conductivity (k Solid ) is calculated and plotted in Figure 2 utilizing a simple analytical model to predict the thermal conductivity of connected graphite networks 15 (Equation (1))…”

“…15) with constants that are universally applied to all foam systems produce results within the uncertainty bounds associated with our density measurements. The bulk density (GF density) and the solid density (graphene ligament density) are both denoted by q where the bulk is measured to be 385 6 70 mg/cm 3 and the ligament value is taken from the literature as 2.2 g/cm 3 . 15 The blue shaded region represents the upper and lower bounds of the estimated ligament conductivity as a function of GF density, where the bounds are determined by the uncertainty in the density measurements.…”