A novel scheme for prediction of deformation mechanisms of block copolymers based on phase behavior

Block copolymers having different strengths of segregation are investigated with respect to their deformation behavior. Disordered block copolymers ar e deformed by the mechanism which corresponds to a glassy homopolymer. A cr azing mechanism is observed for block copolymers with polystyrene as matrix . At the order-disorder transition (ODT), a change from crazing to cavitati on mechanism is observed, confirming the change of deformation mechanism at the ODT. For intermediately and strongly segregated block copolymers, obse rved mechanisms of termination and diversion of crazes are caused by both t he increased long-range order and larger grain size with increasing incompa tibility. A novel scheme is proposed which summarizes the deformation behav ior of block copolymers depending on strength of segregation, chiN. It is n ow possible to predict the deformation mechanism of a diblock copolymer sys tem only from strength of segregation. Since the mechanical properties are also influenced by strength of segregation, it is possible to create materi als with tailored properties utilizing temperature or pressure. The propert y profiles of different block copolymer systems are summarized to demonstra te the exceptional combination of high strength and toughness of intermedia tely segregated block copolymers. The presented scheme only represents a qu alitative picture of deformation behavior of block copolymers and is only a first step to a future predictive modeling.