Abstract
In this work we present a method to manufacture flat sheet membranes with a thin isoporous block copolymer (BCP) layer (thickness <3 µm) by profile roller coating (breadth: 30 cm) on top of a porous support membrane. Highly diluted BCP-solutions were used for this coating process. While we cast membranes with dimensions of 30 cm × 50 cm in this work, the procedure can easily be extended to endless dimensions in this roll to roll (R2R) process. The method offers the possibility to save >95% of BCP raw material compared to common doctor blade casting, by strongly decreasing the layer thickness to below 3 µm in combination with a highly open substructure. Additionally, we report a straightforward method to investigate the influence of the solvent evaporation time between coating and precipitation (phase inversion) on the membrane morphology using one sample only, which also ensures that all other influencing parameters remain constant.
Highlights
Isoporous membranes have been traditionally prepared via ion-track etching [11,12] and inorganic aluminium anodic oxidation (AAO) [13]
While polycarbonate track-etched (PCTE) films suffer from their low pore density, AAO membranes show a high pore density with close hexagonal pore alignment in a range of 50–500 nm interpore distance that comes along with the brittle property of these films
With the aim to reduce the consumption of block copolymer per unit area, in this work highly diluted casting solutions were used in contrast to conventional gap doctor blade cast membranes
Summary
Membrane based separation techniques are used in various industries as water and wastewater treatment [1], gas separation, separation of chemicals and petrochemicals [2], haemodialysis [3] or in clinical sensors [4], in juice production [5], wine filtration [6,7,8], separation of biomolecules [9] or drug delivery [10].Isoporous membranes have been traditionally prepared via ion-track etching [11,12] and inorganic aluminium anodic oxidation (AAO) [13]. First isoporous membranes from self-assembling block copolymers were prepared as thin layers on a solid substrate from solution and transferred to a porous support [14]. A well-known process to generate polymer membranes with a thin selective layer on top of a more open porous spongy substructure from the same material is the non-solvent induced phase separation (NIPS), known as “phase inversion”. This leads to mechanically robust membranes with both good selectivity and high permeance. Applying NIPS to self-assembling block copolymers (so-called SNIPS) can lead to so called integral isoporous membranes if the right conditions are found
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