The preparation of poly(imide-b-amic acid) multiblock copolymers was examined by blending solutions of soluble end-functionalized polyimide and polyamic acid homopolymers. The terminal end groups of the soluble polyimide (PI) and poly(amic acid) (PAA) can react to form a multiblock PI/PAA copolymer that was, subsequently, fully imidized. Atomic force microscopy (AFM) height images showed that surface topography of thin solution-cast films of PI/PAA blends depended strongly on the aging time of the solution. Macroscopically phase-separated structures were seen with short aging times, whereas uniform flat surfaces were seen with increasing aging time. For comparison, mixtures of end-capped PI/PAA (nonreactive) were also prepared that showed macrophase-separated surface structures irrespective of the aging time of the solution. Static light scattering measurements showed an increase in the average molecular weight of the end-functionalized blend of PI/PAA, suggesting the formation of poly(imide-b-amic acid) multiblock copolymers. AFM images in the phase mode and X-ray photoelectron spectroscopy showed that the phase-separated morphology had a much higher surface composition of PI than the blend ratio.