The morphological behavior of a series of well-defined A(2)B simple graft or "Y" architecture block copolymers is characterized via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). This model architecture is formed by grafting a polystyrene block onto the center of a polyisoprene backbone. The volume fraction windows in which specific strongly segregated microphase separated morphologies are observed are shifted to higher volume fractions of the PS graft material than in the corresponding linear diblock copolymers. These findings are in good agreement with recently calculated theoretical phase behavior for simple graft, A(2)B, block copolymers. However, a new morphology, not found in neat linear diblock copolymers, is also observed. This A(2)B material is microphase separated into wormlike micelles but not ordered on a lattice. This morphology is found at high PS graft. volume fraction (phi(s) = 0.81), where the two PI chains per molecule are initially forced to the concave side of the PS/PI interface.