Enhanced Actuation Strains of Rubber Composites by Combined Covalent and Noncovalent Modification of TiO2 Nanoparticles

TiO2 nanoparticles were functionalized by combined covalent and noncovalent modification and subsequently used to enhance actuated strains of acrylonitrile-butadiene rubber (NBR) composites. The TiO2 nanoparticles were first modified by noncovalent deposition of poly(catechol/polyamine) (PCPA) and subsequently functionalized with gamma-(2,3-epoxypropoxy)-propytrimethoxysilane (GPTMS) to form TiO2-PCPA-GPTMS nanoparticles. The PCPA deposition preserved the original surface characteristics of the TiO2 nanoparticles, whereas the epoxy groups of GPTMS provided strong interfacial interaction with the polar rubber. The modified TiO2-PCPA-GPTMS nanoparticles enhanced mechanical, dielectric, and electromechanical properties of NBR composites. Thus, the composite filled with 10 phr TiO2-PCPA-GPTMS showed an approximate actuated strain of 11% under an electric filed of 47 kV/mm, which was about 230% of pure NBR in this study (4.8%). Compared with dopamine modification, the method described herein is cheaper and requires shorter reaction times, and it may have potential applications in industry.