How does Micro‐ and Macro‐Phase Separation of Block Copolymers Affect the Formation of Integral Asymmetric Isoporous Membranes? A Review on Effective Factors

Abstract

Self-standing isoporous membranes based on amphiphilic block copolymers (BCPs) are an outstanding candidate for efficient separation processes. Such fascinating membranes have been generated through combining the BCP self-assembly (micro-phase separation) together with the classical non-solvent induced phase separation (macro-phase separation), known as SNIPS process. However, the controllability, reproducibility, and cost-effectiveness of the process along with the mechanism for pores generation are still challenging in the SNIPS strategy, especially when new BCP or conditions are utilized. It is mainly due to the narrow efficacy window of numerous variables influencing the desired structure formation. In this review, first, an overview of the one-step readily scalable SNIPS technique and the stepwise explanation of the process are given. Then the formation mechanism of SNIPS membranes, according to the related hypotheses and assumptions proposed on the basis of experimental evidence so far, is presented and discussed. As the main focus , governing factors in the SNIPS process which affect the preparation and structural characteristics of final membrane structures are entirely reviewed and interpreted. This review will help to have a better understanding of the connection between determinant factors and final membrane structure, which facilitates successful preparation of BCP membranes via SNIPS.

Microstructure development and mechanical performance of MWCNTs/GNPs filled SEBS with different block content

“…It is well-known that the driving force for phase-separated domain formation, which is the thermodynamic incompatibility between the two blocks, is strong in the absence of a convective field and while cooling. 31,32 It also should be noted that the high viscosity and domain network in the S30 matrix causes further constraints for nanoparticles to move toward each other, significantly hindering particle-particle interactions that are the driving force to form a percolated nanoparticle structure. In other words, favorable interaction between PS block and nanoparticles can reinforce the phaseseparated domain network by enhancing microphase separation at the expense of weakening the nanoparticles' 3D network.…”

Modular Synthesis of Functional Block Copolymers by Thiol–Maleimide “Click” Chemistry for Porous Membrane Formation

“…Thus, SNIPS membranes are considered to be competitive to the commercially used track-etching technique but with the advantage of significantly higher flux due to hexagonal closed-packed cylindrical pores at the surface by self-assembly. The nanopore layer is above a microporous sponge-like structure, in addition to larger caverns, similar to classical NIPS membranes. , Since the introduction of the SNIPS process, many studies on SNIPS membranes dealing with processing conditions, − chemical modifications, − and potential applications ,, have been reported. In addition, the stimuli-responsive behavior of amphiphilic BCPs allows users to tune resulting BCP membrane properties by external triggers. ,,, Moreover, hydroxyl bearing BCPs like polystyrene- b -poly­(2-hydroxyethyl methacrylate) (PS- b -PHEMA) and polystyrene- b -poly­(solketal methacrylate) (PS- b -PSMA) are a major focus of the SNIPS membrane community due to adjustable pore sizes of the selective membrane layer and its ability to fractionate proteins for biomedical application. ,, Schöttner et al developed PS- b -PHEMA SNIPS membranes with a high water flux, and different chemical approaches were investigated to introduce stimuli-responsive moieties by postmodification of PS- b -PHEMA. ,, …”

An anchor for help: a cross-linking moiety for block copolymer membrane stabilization for ultrafiltration applications in water

“…3,4 For more information on this process the authors refer to some recent and seminal reviews in the field. [5][6][7] Negatively, these membranes suffer from poor oxidative/chlorine-, pH-, thermal-and compacting resistance. 8 Within the present study, we aim to increase the compacting resistance of these polymeric membranes.…”