Control of the structure and properties of SEBS nanocomposites via chemical modification of graphene with polymer brushes

Abstract

Incorporation of small quantities of graphene modified with polystyrene brushes into poly (styrene-b-ethylene-co-butylene-b-styrene) (SEBS) produces elastomeric conductive nanocomposites with enhanced electromechanical behaviour. Compared to graphene modified with polyethylene rubbery brushes, polystyrene-modified graphene distorts the hexagonal packing of cylinders in SEBS to a lesser extent due to the selective interactions with the rigid polystyrene blocks. At the same time, the type of filler has an apparent impact in the nano-, macro- and electro-mechanical properties of the nanocomposites. Consistently, AFM nanoindentation shows a narrower distribution of modulus values for the polystyrene modification. Moreover, tensile testing reveals that only the nanocomposites with styrene-affine fillers show elongation at break comparable to SEBS. Most importantly, a stable electromechanical behaviour is only found for the polystyrene modification, which is attributed to the selective interaction of the brushes on graphene with the polystyrene blocks of the matrix. The work offers a comprehensive understanding of the interplay between the nature of the polymer brush grafted to graphene, the nanostructure of the nanocomposites and their final properties.