Simulation of Membrane Fabrication via Solvent Evaporation and Nonsolvent-Induced Phase Separation

Abstract

Block copolymer membranes offer a bottom-up approach to form isoporous membranes that are useful for ultrafiltration of functional macromolecules, colloids, and water purification. The fabrication of isoporous block copolymer membranes from a mixed film of an asymmetric block copolymer and two solvents involves two stages: First, the volatile solvent evaporates, creating a polymer skin, in which the block copolymer selfassembles into a top layer, comprised of perpendicularly oriented cylinders, via evaporation-induced self-assembly (EISA). This top layer imparts selectivity onto the membrane. Subsequently, the film is brought into contact with a nonsolvent, and the exchange between the remaining nonvolatile solvent and nonsolvent through the selfassembled top layer results in nonsolvent-induced phase separation (NIPS). Thereby, a macroporous support for the functional top layer that imparts mechanical stability onto the system without significantly affecting permeability is fabricated. We use a single, particlebased simulation technique to investigate the sequence of both processes, EISA and NIPS. The simulations identify a process window, which allows for the successful in silico fabrication of integral-asymmetric, isoporous diblock copolymer membranes, and provide direct insights into the spatiotemporal structure formation and arrest. The role of the different thermodynamic (e.g., solvent selectivity for the block copolymer components) and kinetic (e.g., plasticizing effect of the solvent) characteristics is discussed.

An Antisolvent Extraction Strategy for Extrusion Granulation Enhancement of Aluminum-Based Lithium Adsorbent Used in Ultrahigh Mg2+/Li+ Salt Lake Brines

“…During the process of antisolvent treatment, the polymer binders loaded with Li/Al-LDH powders immediately changed from a dispersed phase to a continuous phase. Meanwhile, the organic solvent changed to the dispersed phase and rapidly diffused into the water, leaving a large number of specific cavities and pores . Additionally, the adsorption kinetics of GLDH-EA and GLDH-ES are shown in Figure g, and it was found that GLDH-EA exhibited a significantly faster adsorption rate than GLDH-ES in 6 h, attributing to the rapid mass transfer related to the internal pore structure in GLDH-EA.…”

Evaporation-Induced Self-Assembly of Diblock Copolymer Films in an Electric Field: A Simulation Study

“…To effectively simulate evaporation, we employ a conversion zone at the upper boundary of the simulation cell, in which all solvent particles are converted to gas at an interval of 50 MCS. Similar approaches have been previously employed. − , Alternatively, the conversion zone follows the established film surface at a constant distance, d vap , increasing the evaporation rate at later times.…”

“…Similar approaches have been previously employed. [22][23][24]59 Alternatively, the conversion zone follows the established film surface at a constant distance, d vap , increasing the evaporation rate at later times.…”

“…Our simulations provided direct insights into the underlying mechanisms responsible for the controlled evolution of perpendicularly aligned cylinders during the solvent evaporation step in casting block copolymer membranes. Combining these findings with studies of non-solvent-induced phase separation (NIPS) 59 will provide an opportunity to map out the window of thermodynamic and processing parameters that allow for the formation of integral asymmetric membranes. 8,9 ■ ASSOCIATED CONTENT * sı Supporting Information…”

Polyacrylonitrile-containing amphiphilic block copolymers: self-assembly and porous membrane formation

“…18 Within a recent work, Blagojevic and Müller identified the most important influencing parameters using simulations. 29 Although valuable work has been published in this field, 4,19,21 there is still need for improvement regarding the membranes' mechanical stability. Amongst others, 30 our group has approached this issue by incorporating UV-crosslinkable moieties into a methacrylate-based amphiphilic BCP prepared by ATRP, 31 leading to improved solvent resistance and mechanical stability.…”