Improved actuation performance and dielectric strength of natural rubber composites by introducing covalent bonds between dielectric filler and polymeric chains

In this work, polyrhodanine (PRd) was first used to modify titanium dioxide (TiO2) nanoparticles (NPs) (denoted as TiO2-PRd), which were then incorporated into natural rubber (NR) matrix (denoted as TiO2-PRd/NR) to yield dielectric elastomer (DE)-based composites. PRd was polymerized from rhodanine containing abundant acceptor (N-C=S), which was suitable for the formation of covalent bonds between dielectric NPs and NR chains. This improved the interfacial interaction and compatibility between TiO2 NPs and NR matrix, resulting in NR DE-based composites with excellent dielectric properties and electromechanical performance. Among samples, NR DE-based composite filled with 10 phr TiO2-PRd NPs achieved the highest actuated strain of 38.6% at 102 kV/mm. Moreover, the addition of TiO2-PRd NPs resulted in TiO2-PRd/NR-50 DE-based composite with the highest dielectric strength (133 kV/mm), a value of 1.82 times of pure NR (73 kV/mm). In sum, the proposed strategy looks effective and simple for simultaneously improving the electromechanical performance and dielectric strength of NR DE-based composites.