Mechanistic Evaluation of Silane Spacer Length on Mechanical and Dielectric Properties of Polydimethylsiloxane‐Graphene Nanocomposites

ABSTRACT The main challenges of using conductive nano‐fillers in dielectric elastomer composites are the proper dispersion of particles as well as the trade‐off between dielectric permittivity and dielectric loss resulting from the interfacial polarization and the current leak leading to bulk conduction. To address these challenges, the role of the hydrocarbon spacer length of silane grafted on the surface of reduced graphene oxide (RGO) was investigated in this study. For this purpose, RGO was surface‐modified using two silane coupling agents with different hydrocarbon spacer lengths, short‐spacer triethoxypropylsilane (PTEO) and long‐spacer hexadecyltrimethoxysilane (HDTMS), and the effect on the mechanical and dielectric properties of polydimethylsiloxane nanocomposites was evaluated. It was shown that the longer spacer length of silane provides improved dispersion of RGO in PDMS and forms insulating layers that suppress charge leakage and bulk conduction. Composites containing silane with long spacer length exhibited significantly lower dielectric loss, enhanced dielectric breakdown strength, and improved dielectric efficiency compared to both uncoated and short‐spacer length silane. Most notably, the nanocomposite containing silane with long spacer length achieved approximately two times the maximum Maxwell stress, a key parameter related to actuation strain, highlighting the critical role of hydrocarbon spacer length in optimizing the barrier effect and minimizing electron hopping.