Ultraporous Films with Uniform Nanochannels by Block Copolymer Micelles Assembly

Abstract

Films with high pore density and regularity that are easy to manufacture by conventional large-scale technology are key components aimed for fabrication of new generations of magnetic arrays for storage media, medical scaffolds, and artificial membranes. However, potential manufacture strategies like the self-assembly of block copolymers, which lead to amazing regular patterns, could be hardly reproduced up to now using commercially feasible methods. Here we report a unique production method of nanoporous films based on the self-assembly of copper(II) ion-polystyrene-b-poly(4-vinylpyridine) complexes and nonsolvent induced phase separation. Extremely high pore densities and uniformity were achieved. Water fluxes of 890 L m -2 h -1 bar -1 were obtained, which are at least 1 order of magnitude higher than those of commercially available membranes with comparable pore size. The pores are also stimuli (pH)-responsive.

Block Copolymer Membranes for Aqueous Solution Applications

“…The solvents are selective for one of the blocks, favoring micelle formation, following the rules summarized in Figure 5. The role of micelles in the membrane formation was first identified by our group 111 . Their presence and assembly in the solution bulk before casting has been directly confirmed by cryo transmission (TEM) and scanning electron (SEM) microscopy 62,99,111,117,118 and small angle x-ray scattering (SAXS) of the casting solution 99,113,114 .…”

“…The role of micelles in the membrane formation was first identified by our group 111 . Their presence and assembly in the solution bulk before casting has been directly confirmed by cryo transmission (TEM) and scanning electron (SEM) microscopy 62,99,111,117,118 and small angle x-ray scattering (SAXS) of the casting solution 99,113,114 . Indications that the micelle structures remain as part of the ordered top layer of the membrane were presented by different groups 61,111,112 , using scanning (SEM) or transmission (TEM) electron microscopy, with tomography, scanning transmission electron microscopy (STEM) and focus ion beam (FIB).…”

“…The sublayer is shaped by macrophase separation, preferentially guided by spinodal decomposition (SD) as detailed explained for membranes obtained from homopolymers 106,108 . The contribution of spinodal decomposition has been early clearly discussed by our group 99,111 . SD has been recognized by other groups as a component of the mechanism, for instance by Stegelmeier et al 116 .…”

“…Only years after the first report the method could be reproduced with different copolymer batches and solvents then with better understanding of how the morphology develops. By using field emission scanning microscopy, focus ion beam and cryo transmission electron microscopy 61,111 we claimed for the first time that the micelle formation in solution is essential for the membrane formation in this case. Later this has been recognized by other excellent groups in the field 112 .…”

Nanostructured double hydrophobic poly(styrene-b-methyl methacrylate) block copolymer membrane manufactured via a phase inversion technique

“…Previous studies showed isoporous membranes were prepared using di-or trisolvent systems. 10,12,14 Initially, we prepared membranes using mono-and di-solvent mixtures, however, the morphologies of the PS-b-PMMA membranes did not show an ordered pore morphology ( Fig. S1 ESI †).…”