Defect-Mediated Interfacial Polarization in TiO2-Grafted CNT/PDMS Nanocomposites for Terahertz EMI Screening

Achieving tunable terahertz electromagnetic interference screening requires balance between conductive charge transport and dielectric polarization within a nanocomposite architecture. This study investigates conductive−dielectric synergy in flexible hybrid nanocomposites consisting of titanium dioxide decorated carbon nanotube nanofillers dispersed within a polydimethylsiloxane matrix. Four nanocomposites with increasing CNT loadings, namely 0.4, 0.7, 1.0, and 1.3 wt %, are fabricated, with TiO2 content fixed at 10 wt % relative to CNT mass. Their structural, morphological and thermal properties are investigated using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, and thermogravimetric analysis. The dielectric response and charge transport dynamics are probed using an indigenously developed terahertz time-domain spectroscopy system operating over 0.2−1.1 THz, and analyzed through the Drude−Smith model. Raman analysis reveals increasing structural disorder and stronger CNT−TiO2 interfacial coupling with rising filler content. Meanwhile, the scattering time decreases, accompanied by a shift in the localization parameter, signifying enhanced carrier confinement at TiO2-induced defect and interfacial sites as the filler content is increased. This defect-mediated interfacial polarization, coupled with a persistent conductive CNT network, yields a maximum total shielding effectiveness of ∼35 dB. The results establish a direct correlation between Raman-derived structural disorder, Drude−Smith charge-transport parameters, and terahertz screening performance, demonstrating that interfacial polarization at TiO2-grafted CNT junctions and charge transport through the CNT network collectively regulate the terahertz screening response. These findings provide design guidelines for developing lightweight, flexible, and tunable TiO2-grafted CNT/PDMS nanocomposites for next-generation terahertz electromagnetic interference screening applications.