Block copolymers often phase separate. One extensively studied tri- block copolymer is styrene-butadiene-styrene. Consider the following evidence and schematically plot the anticipated stress-strain response of the three copolymer varieties on the same graph.

a) At 13% polystyrene, there is no phase separation.

b) At 28% polystyrene, the copolymer material is a thermoplastic elastomer and elongates to 600% before stiffening significantly.

c) At 80% polystyrene, the copolymer material behaves very much like