Strain-Induced Nanocavitation in Block Copolymer Thin Films for High Performance Filtration Membranes

Abstract

A new pore formation process was investigated for the manufacture of composite ultrafiltration membranes. Phase-separated block copolymer (BCP) thin films supported on a compliant macroporous poly(ether sulfone) (PES) support craze under tensile strain, leaving behind pores of predictable size based on the self-assembled nanoscopic domains. The high aspect ratio pores formed in this process were used to create membranes that were highly permeable (959 L/ (m 2 h bar) with near complete rejection of 40 nm diameter gold nanoparticles (AuNP). By use of BCP's inherent ability to cavitate under strain, tedious block removal steps are avoided. Membranes can thus be prepared in a simple, roll-toroll ready, one-step process. In this initial study, BCP craze formation and filtration performance were characterized for various polymer types, molecular weights, and thicknesses. All these factors influenced the BCP's thin film morphology, mechanical performance, deformation mechanism, and ultimately filtration performance. This work demonstrates a possible new path toward achieving scalable, BCP-based ultrafiltration membranes.

A versatile route for the fabrication of micro-patterned polylactic-acid (PLA)-based membranes with tailored morphology via breath figure imprinting

“…[2][3][4][5][6] Several approaches were developed and used to create nano and/or micro-patterned porous surfaces such as non-solventinduced phase separation (NIPS), vapor-induced phase separation, stretching, 3D printing, and cold zone annealing. [7][8][9][10] However, one of the simple approaches is driven by the interaction between water vapor and a highly volatile solvent on the polymer surfaces. This method is called breath figure (BF) imprinting.…”

Molecular Simulations Revealing Effects of Non-concatenated Ring Topology on Phase Behavior of Symmetric Diblock Copolymers

“…The phase behavior of block copolymers underlies many technological applications that rely on the morphology of block copolymers, such as lithography, water purification, gas permeation, and ion transport in batteries. − Predicting the phase behavior of block copolymers has been celebrated as a triumph of polymer field theory. − Much of the parameter space, including the molecular weight, block composition, enthalpic interaction strength, and polymer architecture, has been extensively explored. One promising direction to expand the parameter space is to replace the conventional linear chains with nonconcatenated rings. − Such an expansion is intriguing due to the distinctive conformations, − dynamics, ,− and material properties − revealed for homopolymer rings in the past two decades and also timely because of the advances in synthesizing and characterizing high-molecular-weight ring polymers. , …”

Polymer Thin Film Necking: Ductility from Entanglements and Plane Stress Condition

“…Recent advances in nanoengineering have enabled sub-100 nm polymer thin films to be fabricated and thus propelled their applications in organic electronics, coating, filtration, and separation technologies. − Many functions of polymer thin films rely on their high strength-to-weight ratio and durability, both highlighting the significance of their mechanical properties. One particularly intriguing observation is that a brittle polymer glass in the bulk state, such as polystyrene (PS), exhibits ductility in the thin film state via the shear deformation resulting from necking. ,, This brings film thickness as a new dimension to the parameter space determining the brittle-to-ductile transition, which is a central topic in glassy polymer mechanics. − The microscopic mechanism of ductile thin film necking needs to be understood to promote the rational molecular design of stretchable and durable polymer thin films.…”