Thermal conductivity of multilayer polymer-nanocomposite thin films

Abstract

The development of electrical insulators that are thermally conducting is critical for thermal management applications in many advanced electronics and electrical devices. Here, we synthesized polymer nanocomposite (PNC) films composed of polymers [polyethylenimine, poly(vinylamine), poly(acrylic acid), and poly(ethylene oxide)] and dielectric fillers (montmorillonite clay and hexagonal boron nitride) by layer-by-layer technique. The cross-plane thermal conductivity [Formula: see text] of the film was measured by the 3ω method. The effect of various factors such as film growth, filler type, filler volume fraction, polymer chemical structures, and temperature on the thermal conductivity is reported. The [Formula: see text] of PNCs with thickness from 37 nm to 1.34 μm was found to be in the range of 0.11 to 0.21 ± 0.02 W m−1 K−1. The [Formula: see text] values were found to be lower than the constituent polymer matrix. The experimental result is compared with existing theoretical models of nanocomposite systems to get insight into heat transfer behavior in such layered films composed of dielectrics and polymers.

Nanobrick Wall Multilayer Thin Films with High Dielectric Breakdown Strength

“…Similar to BMT, it is believed the structure of VMT plays a minimal role in altering the properties of the different nanocomposites, as its characteristic peak does not undergo any noticeable change. When relating structure to property, it is suspected that polymer and platelet crystallinity is not a dictating factor in the thermal conductivity decrease for the dual clay nanocomposite; it is believed that the number of polymer-platelet and platelet–platelet interfaces is causing an increase in phonon scattering, which is reducing the thermal conductivity of the nanocomposite . Furthermore, while the effects of BMT and VMT’s structure and crystallinity on the dielectric properties of the reported systems herein cannot be ruled out, it is believed that the improvement in dielectric properties is due to the significantly higher inorganic loading and the influence of a more tortuous pathway for charge transport when incorporating both platelets.…”

“…The effective thermal conductivity of the nanocomposite, along with the thermal conductivity values of the bulk substrates (undoped silicon) and the nanocomposite at various thicknesses, were determined by fitting the experimental data [temperature amplitude (Δ T ) vs current frequency (Hz)] to the data reduction method proposed by Tong et al (see Figure S3a–c). , The thermal conductivity of the underlying undoped silicon substrate was measured separately as a control and its value of 146.5 ± 5.9 W m –1 K –1 was used in data fitting. In order to determine the effective thermal conductivity of the nanocomposite, a series of films with varying thickness ( t ) were prepared and their thermal resistances ( R ) were obtained.…”

“…The data in Table present a direct relationship between thickness and thermal resistance (i.e., as thickness increases thermal resistance increases). Previous work, which compared experimental results to existing theoretical models, found that thermal boundary resistance at interfaces in LbL-assembled nanocomposites are the dominant factor governing film effective thermal conductivity . As thickness is increased, it is believed that the amount of interfaces (between platelets and the polymer matrix) also increases, leading to a lower thermal conductivity due to more interfacial thermal resistance.…”

“…It is believed that these LbL films, containing a tortuous path created by nanoplatelets, will greatly help improve the dielectric properties if loaded with electrically insulating fillers. While LbL assembly of polyelectrolyte-based composites has been investigated for dielectrics and thermal conductivity independently, ,, a nanocomposite created to exploit both of these properties has yet to be investigated.…”

Dual Clay Nanobrick Wall Thin Films with High Oxygen Barrier at High Humidity

“…[6,7] Layer-by-layer (LbL) assembly is an attractive alternative to vapor deposited and extruded barriers due to its aqueous solution-based deposition, ambient processing conditions, and nanoscale control over thickness. [8][9][10][11] LbL assembly typically consists of the alternate deposition of oppositely charged macromolecules (i.e., polyelectrolytes) and/or nanoparticles on the surface of a charged substrate. This process can consist of a number of cycles, varying in the number of layers in the deposition pattern (e.g., bilayer, quadlayer, or hexalayer).…”