Modeling Microstructure Formation in Block Copolymer Membranes Using Dynamical Self-Consistent Field Theory

Area of Science:

• Polymer science
• Materials science
• Chemical engineering

Background:

• Block copolymers are promising for ultrafiltration membranes due to self-assembly and nonsolvent-induced phase separation (SNIPS).
• Understanding the relationship between processing variables and membrane morphology is critical for optimizing performance.
• The interplay between microphase and macrophase separation during SNIPS in block copolymers is not fully understood.

Purpose of the Study:

• To investigate the microstructure evolution of block copolymer films during SNIPS.
• To determine the influence of solvent and nonsolvent selectivity on membrane morphology.
• To elucidate the conditions necessary for forming isoporous integral-asymmetric membranes.

Main Methods:

• Dynamical self-consistent field theory simulations were employed.
• Simulations focused on the microstructure evolution of block copolymer films during the SNIPS process.
• Analysis centered on the impact of solvent and nonsolvent block selectivities.

Main Results:

• Block copolymer films formed the desired sponge-like asymmetric porous substructure only when the solvent and nonsolvent exhibited opposite block selectivities.
• When solvent and nonsolvent had similar block selectivities, dense, nonporous, microphase-separated films were produced.
• The study highlights the critical role of solvent-nonsolvent interactions in controlling membrane architecture.

Conclusions:

• The choice of solvent and nonsolvent is a key determinant in fabricating effective block copolymer ultrafiltration membranes.
• Opposite block selectivities are essential for achieving the desired porous structure via SNIPS.
• These findings provide critical guidance for the rational design and processing of advanced block copolymer membranes.