This work demonstrated the combination of the self-assembly of a block copolymer with the well-established non-solvent induced phase separation process.Nanoporous films were obtained with well-ordered cylinder pores perpendicular to the film surfaces on top of a non-ordered bicontinous porous layer.Numerous parameters during the film formation process

including the concentration of casting solution

the solvent evaporation time

the temperature of precipitation bath

and the gate height of doctor blade

were systematically investigated to realize the effective control of surface morphology.Voronoi tessellation was first introduced to quantitatively describe the regularity of the surface pattern.It was found that the concentration of casting solution and the solvent evaporation time have synergetic influences on the porous structures.With the increase of concentration

the minimum evaporation time needed for a well-ordered porous surface decreases.If keep the concentration as a constant

the evolution of surface morphologies from non-ordered cylinder pores to ordered cylinder pores

and then to lamellar pores

was observed with the increase of evaporation time.Although lots of combinations of these two parameters can be utilized for the well-ordered structure formation

the mean pore size of the film surface didn't change significantly with the change of film preparation conditions.Besides

the decrease of the temperature of precipitation bath also helped to improve surface pattern regularity.Further study revealed that once the gate height of casting solution was decreased

the evaporation of solvent induced more significant change of casting solution concentration and the solvent composition

resulting in the disappearance of well-ordered cylinder pores.Two ways

including decreasing the solvent evaporation time and applying the solvent annealing process

were proven to be very effective to prepare thinner films with well-ordered nanoporous structures.The above results greatly broaden the operation window and provide possibilities to fabricate films suitable for different applications.