A controllable way to measure the interfacial strength between carbon nanotube and polymer using a nanobridge structure

Abstract

The interfacial strength between an embedded carbon nanotube (CNT) and a polymer matrix is a direct indicator of the interfacial load transfer which significantly impacts the effective mechanical properties of CNT/polymer nanocomposites. However, unavoidable kinks or entanglement of the CNTs in the polymer may complicate the characterization of the interface as measured through nanopullout experiments. In the current work a CNT/polymer nanobridge structure in a suspended polymer film is developed to allow the observation of the embedded portion of the CNT after the pullout process. The nanobridge structure was created on the basis of phase separation of a polymer blend, self-assembly of the CNTs in liquid flow, and ductile fracture of the polymer under thermal and solvent treatment. This structure accommodates a nanomechanical interfacial characterization method where a transverse force applied on the suspended CNT using an atomic force microscope results in an axial pullout force, which is obtained by the force-distance curves and a force balance relation. The high resolution of the AFM in the loading process and the ability to observe the embedded portion of the CNT eliminate uncertainties of the nanopullout process and provide a more controllable approach for measuring the interfacial strength in CNT/polymer nanocomposite systems.