Diblock Copolymer Reinforced Interfaces between Amorphous Polystyrene and Semicrystalline Polyethylene

Abstract

The effects of molecular architecture on the fracture properties of semicrystalline polymers were probed at diblock copolymer-reinforced interfaces between polystyrene (PS) and polyethylene (PE). The PE used for this study was a model ethylene−butene copolymer which was chosen for its compatibility with hydrogenated 1,4-polybutadiene. This compatibility allowed the use of hydrogenated poly(styrene-b-1,4-tetradeuteriobutadiene) as the block copolymer. For a series of these diblock copolymers, the areal chain density (Σ) and the molecular weight of the PE block (Mn) were varied systematically to observe their effects on the interfacial fracture energy (Gc). At low Σ, Gc stayed relatively constant, and was roughly 1 J/m2. Above a critical value of Σ, the fracture energy climbed rapidly. This critical value decreased with increasing Mn. The detection of deuterium on the fracture surfaces indicated that pullout of the PE block was the predominant failure mechanism when Mn ≤ 30 kg/mol. Only when the molecular w...