Hollow fiber spinning of block copolymers: Influence of spinning conditions on morphological properties

The self-assembly of block copolymers proposes interesting strategies for design and fabrication of ordered nano/microdomain structures. Recently, large attention has been given to the preparation of integral asymmetric flat sheet membranes with cylindrical domains forming an isoporous top layer. In this work, this strategy is extended to the formation of nanoporous hollow fiber membranes from polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) solutions via phase inversion process. In this way, the self-assembly of block copolymers into an ordered morphology via solvent evaporation is combined with microdomain alignment by shear flow in the die. The influence of the experimental parameters on the morphology of the hollow fiber is discussed, such as solution concentration and viscosity, extrusion pressure within the spinneret and air gap distance between the spinneret and the precipitation bath (evaporation time). The evaluation of the surface morphology of the membranes by scanning electron microscopy (SEM) confirms the strong effect of shear flow and solution viscosity on the formation of nanoporous structures in hollow fiber spinning.