The influence of solvent removal rate on the morphology of DMF annealed cylinder-forming poly-(styrene-block-4-vinylpyridine) (PS-b-P4VP) thin films with different thickness is investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM).It is found that the final film morphology can be effectively modulated by controlling the solvent removal rate of the swollen film.When the film thickness was 35 nm

under fast solvent removal rate

long range ordered inverted parallel PS cylinders were obtained

as solvent removal rate decreased

the ring-shaped PS nanostructure formed in the whole film

and finally slow solvent removal rate resulted in terrace lamella morphology.Such morphological transformation is mainly due to kinetic effect and preferential affinity of annealing solvent for the minority block

which brings remarkable solvation effect.The unique ring-shaped morphology is caused by the shrinkage of the continuous P4VP phase and bending of the PS cylinders.While when the film thickness was 55 nm

only P4VP cylinder morphology was obtained under the same annealing condition and solvent removal rate.We consider that the low swollen rate will reduce solvation effect when the film is thick

in the mean time the effect of solvent removal rate on the final morphology is weakened.