  We consider micro- and macro- phase separation in blends of AB and BC diblock
copolymers. We show that, depending on architecture, a number of phase diagram
topologies are possible. Microphase separation or macrophase separation can
occur, and there are a variety of possible Lifshitz points. Because of the rich
parameter space, Lifshitz points of multiple order are possible. We demonstrate
Lifshitz points of first and second order, and argue that, in principle, up to
5th order Lifshitz points are possible.
