Synthesis and properties of near IR induced self-healable polyurethane/graphene nanocomposites

A series of self-healable polyurethane (SHPU)/modified graphene (MG) nanocomposites were synthesized from poly(tetramethylene glycol) (PTMG) and 4,4′-methylene diphenyl diisocyanate (MDI) with minute amounts (0–1 wt%) of MG which was chemically modified graphene oxide (GO) with phenyl isocyanate and reduced in the presence of phenylhydrazine. MG gave dual effects of reinforcing filler and light absorption medium. That is, SHPU/MG nanocomposites showed significantly enhanced Young’s modulus and near infrared (NIR) absorption along with increased glass transition temperature (Tg). However, break strength and break strain decreased at high GO contents (MG075, MG100) implying that MG disturbs chain orientations. The self-healing behavior of nanocomposites was done by intermolecular diffusion of polymer chains which was accelerated by thermal energy generated by NIR absorptions. The self-healing effect was most pronounced with 0.75 wt% MG (MG075) where the elastic strain energy was even greater than the fresh material up to over 200% strain. Further addition of MG (MG100) induced more light absorption, but physically disturbed the interchain diffusion to reduce the self-healing efficiency.