Testing the minimum thermal conductivity model for amorphous polymers using high pressure

Pressure dependence of thermal conductivity provides a critical test of the validity of the model of the minimum thermal conductivity for describing heat transport by molecular vibrations of an amorphous polymer. We measure the pressure dependence of the thermal conductivity of poly(methyl methacrylate) (PMMA) brushes grafted from SiC substrates using a combination of time-domain thermoreflectance and SiC anvil cell techniques. We also determine the pressure dependence of the thermal conductivity from a computational model of amorphous polystyrene. In both cases, thermal conductivity as a function of pressure is accurately predicted by the minimum thermal conductivity model via the pressure dependence of the elastic constants and density.