Greatly Enhanced Electromagnetic Interference Shielding Effectiveness and Mechanical Properties of...

Nowadays, evolutions in wireless telecommunication industries, such as the emergence of complex 5G technology, occur together with massive development in portable electronics and wireless systems. This positive progress has come at the expense of significant electromagnetic interference (EMI) pollution, which requires the development of highly efficient shielding materials with low EM reflection. The manipulation of MXene surface functional groups and, subsequently, incorporation into engineered polymer matrices provide mechanisms to improve the electromechanical performance of conductive polymer composites (CPCs) and create a safe EM environment. Herein, Ti₃C₂T MXene nanoflakes were first synthesized and then, taking advantage of their abundant surface functional groups, polyaniline (PA) nanofibers were grafted onto the MXene surface via oxidant-free oxidative polymerization at two different MXene to monomer ratios. The electrical conductivity, EMI shielding effectiveness (SE), and mechanical properties of poly (vinylidene fluoride) (PVDF)-based CPCs at different nanomaterial loadings were then thoroughly investigated. A very low percolation threshold of 1.8 vol % and outstanding electrical conductivities of 0.23, 0.195, and 0.17 S/cm were obtained at 6.9 vol % loading for PVDF-MXene, PVDF-MX₂AN₁, and PVDF-MX₁AN₁, respectively. Compared to the pristine MXene composite, surface modification significantly enhanced the EMI SE of the PVDF-MX₂AN₁ and PVDF-MX₁AN₁ composites by 19.6 and 32.7%, respectively. The remarkable EMI SE enhancement of the modified nanoflakes was attributed to (i) the intercalation of PA nanofibers between MXene layers, resulting in better nanoflake exfoliation, (ii) a large amount of dipole and interfacial polarization dissipation by constructing capacitor-like structures between nanoflakes and polymer chains, and (iii) augmented EMI attenuation via conducting PA nanofibers. The surface modification of the MXene nanoflakes also enhanced the interfacial interactions between PVDF chains and nanoflakes, which resulted in an improved Young's modulus of the PVDF matrix by about 67 and 46% at 6.9 vol % loading for PVDF-MX₂AN₁ and PVDF-MX₁AN₁ composites, respectively.