Abstract The characteristics of structures induced by drying and phase separation in cast films of three poly(siloxane-imide) (PSI) multiblock copolymers are investigated by microscopy and small-angle scattering techniques. Rapid removal of solvent from thin films produces non-equilibrium Benard cells with periodicity between 10 and 20 μm, as determined from light microscopy and scanning electron microscopy. Small-angle neutron scattering (SANS) is used to discern the periodicities and sizes of microstructural elements arising from microphase separation. Scattering curves obtained from solution-cast films indicate that these elements possess periodicities between 15 and 22 nm, depending on molecular architecture, and appear similar to the curves obtained from melt-pressed films. Micrographs of one of the solution-cast materials, obtained with transmission electron microscopy, reveal a disordered biphasic morphology consisting of dispersed imide domains, whose mean size and periodicity are ca 4 and 15 nm, respectively, in excellent agreement with results from SANS.