Abstract: The toughening system of poly(phenylene oxide) (PPO) blends with hydrogenated styrene-bu-tadiene block elastomer(SEBS) and a version grafted with maleic anhydride(SEBS-g-MA) was investigat-ed.Dfferential scanning calorimeter thermograms demonstrated that PPO was miscible with SEBS, whichshowed a unique T_g, but PPO was partially compatible with SEBS-g-MA because there were two of T_g.Toughness research revealed that PPO/SEBS blends achieved litter higher notched Ized impact strengththan pure PPO.However, SEBS-g-MAcould toughen PPO effectively and the blends reached supertoughness with a notched Izod impact strength of 1260J/m at the SEBS-g-MA content of 20%.Trans-mission electron microscopy showed a typical "sea-island" structure in PPOdomain.However, SEBS-g-MA demonstrated a network structure in PPOmatrix.Toughness improvement for PPOblends withSEBS-g-MAwas contributed to stress releasing in micro-cavity.The rheological properties study revealedthat the apparent viscosity of PPO/SEBS blends was improved with the increasing of SEBScontent, butopposite for PPO/SEBS-g-MA blends.

Key words: Poly(phenylene oxide), SEBS-g-MA, Toughening, Miscibility, Submicro-phase