Effect of Asymmetric Lobe Size on the Molecular Dynamics, Glass Transition, and Dielectric Behavior in Janus Nanoparticles

Janus nanoparticles (JNPs) characterized by their two-lobe asymmetrical structures serve as an exclusive platform for customizing the dielectric properties of materials. This investigation explores the influence of poly(3-(trimethoxysilyl)propyl methacrylate) (PTSPM) lobe size variations on the dielectric behavior of JNPs, employing dielectric spectroscopy across a wide temperature range. Initial analysis of seed polystyrene (PS) nanoparticles (NPs) displays characteristics typical of nonpolar polymers, indicating low dipolar activity in their frequency-dependent permittivity (ε′(f)) profiles. However, with the addition of PTSPM, snowman-shaped PS–PTSPM JNPs exhibit heightened dipolar behavior, tapering at higher frequencies owing to PTSPM’s low dipole-frequency response. Temperature-dependent permittivity (ε′( T )) profiles unravel a distinct β-relaxation process at lower temperatures, linked to localized motions within the PTSPM polar lobe. As the PTSPM lobe size increases, this relaxation proportionally intensifies, displaying increasingly larger activation energies. Remarkably, shifts in glass transition temperatures ( T g ) in the JNPS series suggest hindered motions of PS chains in the PS lobe, attributed to the growth of the PTSPM lobe. This systematic investigation reveals a correlation between the asymmetric architecture of JNPs and their dielectric behavior, shedding light on the underlying mechanisms behind the observed variations. Also, synthesizing surfactant-free JNPs assumes paramount importance, as the cleanliness of the interface significantly influences the dielectric properties of these NPs. By exploring the interplay between PTSPM lobe size, molecular dynamics, and glass transition temperatures, this study provides valuable insights into tailoring dielectric properties for advanced functional materials.