Achieving polydimethylsiloxane/carbon nanotube (PDMS/CNT) composites with extremely low dielectric loss and adjustable dielectric constant by sandwich structure

Sandwich-structured composites of polydimethylsiloxane/carbon nanotube (PDMS/CNT) bulk between two neat PDMS thin films with different thicknesses are prepared by the spin-coating method. Taking advantage of CNT's percolation behavior, the composite keeps relatively high dielectric constant (epsilon' = 40) at a low frequency (at 100 Hz). Meanwhile, due to the existence of PDMS isolated out-layers which limits the conductivity of the composite, the composite maintains an extremely low dielectric loss (tan delta = 0.01) (at 100 Hz). Moreover, the same matrix of the outlayer and bulk can achieve excellent interfacial adhesion, and the thickness of the coating layer can be controlled by a multi-cycle way. Then, based on the experimental results, the calculation combining the percolation theory and core-shell model is used to analyze the thickness effect of the coating layer on epsilon'. The obtained relationship between the epsilon' of the composite and the thickness of the coating layer can help to optimize the sandwich structure in order to obtain the adjustable epsilon' and the extremely low tan d. Published by AIP Publishing.