Atomic force microscopy (AFM) has been used to study tethered polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) and polystyrene-b-poly(methyl acrylate) (PS-b-PMA) brushes on flat substrates. The PS-b-PMMA surface was smooth after treatment with CH2Cl2; treatment with cyclohexane led to a relatively rough surface, more obvious in a brush with a thinner PMMA layer. PS-b-PMA brushes exhibited a different nanomorphology after treatment with CH2Cl2, which is may be due to the higher Flory-Huggins interaction parameter between PS and PMA. Treatment of a PS-b-PMMA brush with 30 nm PS and 10 nm PMMA with mixed solvents of CH2Cl2 and cyclohexane resulted in a variety of morphologies including a smooth surface, a rough surface, a very rough surface with irregular structures, and a very rough surface with an unusual nanomorphology. The morphological scale was dependent on the thickness of the tethered diblock brushes.