Soft hybrid elastomers containing polymer grafted nanoparticles

Abstract

Soft elastomers containing inorganic nanoparticles are of interest for uses in soft robotics and flexible electronics, and successful implementation into these applications require enhanced material toughness while maintaining low moduli and high recovery. Controlling nanoparticle dispersion in hybrid materials is necessary to tune physical properties, yet many synthetic methods used to create filled rubbers often lead to macrophase separation. Therefore, alternative synthetic methods are required. Here, we report the synthesis of hybrid elastomers containing polymer grafted nanoparticles (PGNPs) covalently bound to a rubbery matrix. Specifically, poly(norbornene) grafted silica nanoparticles are initially dispersed in a lauryl methacrylate monomer and crosslinker mixture, and then polymerized to create the hybrid elastomer. The polymerization process, termed reaction-induced phase transitions (RIPT), to simultaneously crosslink and trap the nanoparticles in the polymer matrix is a versatile method for preparing soft hybrid elastomers. With increasing nanoparticle loading (e.g., 0 to 10 wt%), PGNP aggregates begin to form and there is an increase in the modulus. Interestingly, there is minimal impact on elastic recovery with respect to PGNP loading as compared to that of the neat, crosslinked matrix. As reported here, the RIPT process is easily adaptable to crosslinked rubbery matrices, highlighting the versatility of the process.