Computer Simulations on the Channel Membrane Formation by Nonsolvent Induced Phase Separation

Abstract

separation happens. After a certain period of phase separation, the polymer-rich phase is solidified as a membrane matrix, and the nonsolvent phase develops pore structures. The polymer concentration and nonsolvent evaporation rate are both critical factors in the phase separation process and porous structure formation. [12] Recently, a technique combining the block copolymers self-assembly and NIPS, termed as SNIPS, has attracted much attention because it yields highly ordered pores from fast one-step preparation process without any mass loss and postprocess. One of the most commonly used diblock copolymers to form ultrafiltration membrane through the SNIPS technique is polystyrene-block-poly (4-vinylpyridine) (PS-b-P4VP). Peinemann et al. [13] first reported this straightforward and very fast one-step procedure for membrane formation. Karunakaran et al. [14] investigated the effects of the solvent system and block length on the self-assemble of poly(styreneblock-polyethylene oxide) (PS-b-PEO) and found that membranes with regular porous structures only formed under the condition of specific block lengths and mixture solvents.Recently, lots of materials have been successfully fabricated into nanoporous membranes via SNIPS, such as PS-b-P2VP, [15] PS-b-P4VP, [16,17] PS-b-PEO, [18] and PS-b-PAA. [19] Preparing membrane with regular porous structure and controlling the pore sizes continue to be challenging these days. At present, some experimental methods can strictly evaluate the pore size, [20] and most SNIPS-manufactured membranes have pore size ranging between 20 and 70 nm. [12] In order to achieve nanofiltration or ultrafiltration, some strategies have been employed, such as adjusting pH, [21] postchemical functionalization, [22] and coating block copolymers onto the supporting membrane, [23] etc. For simple and economical production, we need to control the pore structure and size by adjusting the processing conditions. It is important to mention that the block copolymer assembled in solution is very sensitive to the polymer concentration.The theoretical simulation research may provide valuable microscopic insights and complement to experimental studies on the porous membrane preparation. At present, according to different temporal and spatial scales, scientists have developed different computational and theoretical methods, including the all-atom molecular dynamics, [24] coarse-grained molecular dynamics, [25] Monte Carlo, [26] self-consistent field theory, [27] dynamic density functional theory, [28] dissipative particle dynamics (DPD), [29] and Brownian dynamics, [30] etc. Recently, DPD has attracted more and more attentions as a versatile Block CopolymersThe formation of channel membrane of polystyrene-block-poly(4-vinyl pyridine) block copolymer is studied by computer simulations with the nonsolvent induced phase separation (SNIPS) method. Dissipative particle dynamics is employed to study the microphase separation process and the SNIPS mechanism. Simulation results indicate that polymer concentration has...

DPD Modelling of the Self- and Co-Assembly of Polymers and Polyelectrolytes in Aqueous Media: Impact on Polymer Science

“…This method, called non-solvent-induced phase separation (NIPS), was successfully applied by a couple of experimental groups [248][249][250][251]. Several authors used DPD to confirm the self-assembling mechanism of NIPS proposed by experimentalists, focusing on the effects caused by the concentration, lengths of blocks and others on the structure, regularity and stability of the prepared membranes [252][253][254][255].…”

Next-Generation Ultrafiltration Membranes Enabled by Block Polymers

“…Nanoscale diffusion experiments, such as pulsed field gradient NMR, can directly monitor the tracer diffusion of isotopically labeled water through the membrane pores to investigate the presence of misaligned and discontinuous pores, estimate the pore tortuosity, and reveal nanoscale confinement effects . Finally, simulations that accurately describe the non-equilibrium morphologies obtained after block polymer coating can illuminate nanostructure development. , Such advances can reveal the factors currently limiting the water permeability of block polymer membranes and guide the development of higher performing systems.…”

DL_MESO_DPD: development and use of mesoscale modelling software

“…Further applications involving dl meso dpd as the DPD simulation engine have made use of the same technique of parameterising conservative interactions by finding energies of mixing or Hildebrand solubility parameters using atomistic molecular dynamics or Monte Carlo simulations. These include systems involving carbon nanotubes [100,101], Nafion [102][103][104], block copolymers with poly(carboxybetaine) and poly(ethylene glycol) [105], poly(amido amine) (PANAM) dendrimers and single-stranded DNA [106], poly(methyl methacrylate-co-butyl acrylate-co-styrene) for strengthening fragile papers [107], channel membranes of polystyrene-block -poly(4-vinyl pyridine) block copolymer [108] and phase behaviour of sophorolipids [109].…”