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 (TiO 2 ) nanoparticles (NPs) (denoted as TiO 2 -PRd), which were then incorporated into natural rubber (NR) matrix (denoted as TiO 2 -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 TiO 2 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 TiO 2 -PRd NPs achieved the highest actuated strain of 38.6% at 102 kV/mm. Moreover, the addition of TiO 2 -PRd NPs resulted in TiO 2 -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. • PRd participated in the vulcanization of NR, leading to formation of covalent bonds between filler and matrix. • Improved interfacial interaction resulted in the NR composites with excellent electromechanical performance. • NR composite filled with 10 phr TiO 2 -PRd NPs achieved the highest actuated strain of 38.6% at 102 kV/mm. • The covalent bonds between the filler and matrix led to substantial improvement in the dielectric strength of NR composites.