Block copolymer (BCP)-derived asymmetric ultrafiltration membranes combine the BCP self-assembly with nonsolvent-induced phase separation (SNIPS). To understand the structural evolution in membrane top separation layers made from polyisoprene-b-polystyrene-b-poly(4-vinylpyridine) (ISV) in dioxane (DOX) and tetrahydrofuran (THF) all the way to the final membrane, we combined solution small-angle X-ray scattering (SAXS), estimated solution concentrations and compositions upon solvent evaporation, in situ grazing-incidence SAXS (GISAXS), spin-spin relaxation time (T-2) analysis by solution H-1 NMR, and scanning electron microscopy (SEM). Above the critical micelle concentration (<1 wt % ISV), solvent evaporation drives micelles with poly(4-vinylpyridine) (P4VP) in the core across disorder-to-order and order-to-order transitions, the latter in part driven by the segregation of polyisoprene (PI)- from polystyrene (PS)-blocks. Extended to polystyrene-b-poly(4-vinylpyridine) (SV) in dimethylformamide (DMF) and THF, results suggest that, in particular, T-2 relaxation analysis by H-1 NMR is a powerful tool in analyzing which blocks form micelle core and which form corona chains. We expect insights to help develop next-generation SNIPS membranes for applications, e.g., in clean water and biopharmaceutical separations.