Abstract
The conventional fabrication of isoporous membranes via the evaporation-induced self-assembly of block copolymers in combination with non-solvent induced phase separation (SNIPS) is achieved under certain environmental conditions. In this study, we report a modification in the conventional fabrication process of (isoporous) flat sheet membranes in which the self-assembly of block copolymers is achieved by providing controlled evaporation conditions using gas flow and the process is introduced as gSNIPS. This fabrication approach can not only trigger and control the microphase separation but also provides isoporous structure formation in a much broader range of solution concentrations and casting parameters, as compared to fabrication under ambient, uncontrolled conditions. We systematically investigated the structure formation of the fabrication of integral asymmetric isoporous membranes by gSNIPS. A quantitative correlation between the evaporation conditions (causing solvent evaporation and temperature drop) and the self-assembly of block copolymers beginning from the top layer up to a certain depth, orientation of pores in the top layer and the substructure morphology has been discussed empirically.
Highlights
Block copolymers, their self-assembly and the self-assembled structures have been researched categorically in the last decades, exploring their vast potential in various fields [1,2,3,4,5,6,7,8,9,10]
The desired morphology during the non-equilibrium self-assembly of block copolymers is found only in a narrow range of parameters and that must be fixed by non-solvent induced phase separation (NIPS); the overall process of self-assembly of block copolymers followed by NIPS is abbreviated as the SNIPS process [23]
The study of isoporous membrane fabrication using polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer showed that the critical conditions required for isoporous structure formation exist in a narrow window of solution composition and fabrication conditions, various transient morphologies could be seen in the path to achieving a regular pore network with the further possibility of structural changes [28]
Summary
Their self-assembly and the self-assembled structures have been researched categorically in the last decades, exploring their vast potential in various fields [1,2,3,4,5,6,7,8,9,10]. The study of isoporous membrane fabrication using polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer showed that the critical conditions required for isoporous structure formation exist in a narrow window of solution composition and fabrication conditions, various transient morphologies could be seen in the path to achieving a regular pore network with the further possibility of structural changes [28]. This is comparatively less complex in the case of highly segregated polystyrene-block-poly(4-vinylpyridine)
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