Thermal conductivity of tunable lamellar aluminum oxide/polymethyl methacrylate hybrid composites

We prepared hybrid aluminum oxide (Al2O3)/polymethyl methacrylate (PMMA) composites with tunable lamellae, produced through a two-step synthetic method: fabrication of inorganic scaffolds via ice-templating, followed by organic infiltration polymerization as a substitute for the sublimed ice. The final lamellar hybrid products show anisotropic physical properties. The thermal conductivity in both principal directions was determined for three different samples as a function of temperature (∼3 K–300 K). Typical room temperature thermal conductivities are in the range of 0.5–2.5 W/(m K), depending on the composition and direction. Across the lamellae, the thermal conductivity is well modeled by a linear series of thermal resistors, and along the lamellae it is well represented by parallel thermal resistors of continuous slabs of PMMA and ∼200-μm long slabs of Al2O3, joined by PMMA. From the thermal conductivity perspective, the Al2O3/PMMA composite is a nacre mimic.