Asymmetric poly(1,1-dimethyl silacyclobutane)-block-polystyrene-block-poly(2-vinyl pyridine) (PDMSB-b-PS-b-P2VP) thick films, consisting of a spongelike substructure topped by a nanostructured dense top layer, were produced by combining a fast self-assembly of the triblock terpolymer chains with nonsolvent-induced phase separation (referred as SNIPS). A controlled evolution of the thickness and morphology of the nanostructured top layer was achieved upon solvent vapor annealing (SVA). For instance, the sub-100 nm thick square array morphology generated by SNIPS is transformed into a 1.5 mu m thick core-shell perforated lamellar (PL) structure when exposed to a chloroform (CHCl3) vapor for 3 h. A PL phase having highly ordered continuous P2VP nanochannels can be envisioned as an appealing morphology for membrane applications, since such a network structure formed on asymmetric PDMSB-b-PS-b-P2VP thick films obviates the need for alignment. Monoliths entirely composed of the bicontinuous PL structure were also produced by increasing the duration of the SVA treatment (18 h, CHCl3).