The influence of coiled nanostructure on the enhancement of dielectric constants and electromagnetic shielding efficiency in polymer composites

We report through a comparison of the electromagnetic properties of polymer composites constituted of linear and nonlinear (helically coiled) carbon nanotubes (CNTs) that the electromagnetic interference (EMI) shielding efficiency could be much increased in the latter. A higher ac conductivity and relative dielectric permittivity (both ε ′ and ε ″ ) was recorded when coiled structures were used, and was ascribed to enhanced capacitive and electric field depolarization effects. The EMI shielding was related to the extended length/diameter aspect ratio of the CNTs. Our study has implications in the design of materials for EMI shielding, where nanostructure geometry could play a major role.