The thiol group modified multi-wall carbon nanotubes to enhance the dielectric properties of polystyrene

The researches on how to prepare the polymer composites with high dielectric constant (high-k) and low dielectric loss were important for the rapid development of electronic industry. In this paper, by using silane coupling agent, the multi-wall carbon nanotubes (MWCNTs) could graft the thiol groups with high chain transfer constant on the surface, which made the polystyrene (PS) chain coat more efficiently on the surface of MWCNTs to form the core-shell structure. 1H NMR, TGA and TEM results, showed polystyrene were grafted on the surface of MWCNTs. The grafted PS could reduce the dielectric loss of composite materials and promote the dispersion of the coating MWCNTs in the matrix. In addition, the insulating layer effectively improved the interaction between the MWCNTs and PS matrix, which strengthened the binding force between the filler and matrix, resulting in the increase of the thermal stability of the PS composites. In terms of AC conductivity, the insulating layer could effectively prevent the contact between adjacent MWCNTs from forming a complete conducting network, which inhibited the generation of leakage current. Therefore, compared with untreated multi-wall carbon nanotubes/polystyrene composites, the above composites had excellent dielectric properties with high dielectric constant (214) and low dielectric loss (2.23) at low CNTs mass fraction (4 wt%).