Fabrication Of High-K Polymeric Composites With Low Dielectric Loss Based On Cross-Linked Divinylbenzene Coated Multiwalled Carbon Nanotubes

With the development of novel storage devices, industrial communities raise higher demand on dielectric properties of the material. Percolating insulator/conductor polymer composites have attracted much attention in recent years because of their intrinsic advantages of low density, easy processing and excellent mechanical properties. However, insulator/conductor materials often present large dielectric loss as a result of high leakage currents caused by direct contact between conductive fillers in composites near the percolation threshold, which hinders their further application. Our work mainly focused on the coating of conductive MWCNTs. The main tasks we have completed are as followings:1. Multiwalled carbon nanotubes (MWCNTs) coated by cross-linked divinylbenzene (DVB) shells were synthesized by direct, in situ free-radical polymerization via a controlled manner, thereby producing a core-shell microstructure with an MWCNT center hybrids. The shell thickness of the prepared DVB-coated MWCNTs could be varied from 5 nm to as high as 80 nm by controlling the weight ratio of monomers2. By adding MA as the "second" monomer, we successfully prepared cross-linked DVB-MA copolymer coated MWCNTs in situ free-radical polymerization via a controlled manner. The polymer shell thickness could be controlled from 10 nm to 40 nm by means of tuning the weight ratio of initiator, solvent and substrate concentration. FTIR, XPS characterization proves the existence of acid anhydride groups.3. The prepared DVB@MWCNTs hybrids with different length and coating layer thickness were compounded with polystyrene and epoxy resin respectively. It turns out that dielectric properties of the composite can be tuned by coating layer thickness. By choosing fillers with particular thickness coating layers, we successfully fabricated composites with excellent dielectric properties which possess high dielectric constant and low dielectric loss.4. The prepared DVB-MA@MWCNTs hybrids with different coating layer thickness were compounded with TPU. Through the investigation by ATR-IR, XRD and LCR, the fabricated elastomer shows good mechanical and dielectric properties and the acid anhydride groups improve the interface compatibility between MWCNTs and TPU matrix.