Self-Assembling Zwitterionic Copolymers as Membrane Selective Layers with Excellent Fouling Resistance: Effect of Zwitterion Chemistry

Abstract

Membranes with high flux, ∼1 nm pore size, and unprecedented protein fouling resistance were prepared by forming selective layers of self-assembling zwitterionic amphiphilic random copolymers on porous supports by a simple coating method. Random copolymers were prepared from the hydrophobic monomer 2,2,2-trifluoroethyl methacrylate (TFEMA) and four zwitterionic monomers (sulfobetaine methacrylate, sulfobetaine 2-vinylpyridine, sulfobutylbetaine 2-vinylpyridine, and 2-methacryloyloxyethyl phosphorylcholine) by free radical polymerization. All copolymers microphase separated to form bicontinuous ∼1.2 nm nanodomains with the zwitterionic domains acting as nanochannels for the permeation of water and solutes. The resultant membranes all had a ∼1 nm size cutoff independent of zwitterion chemistry. There were, however, significant differences in the hydrophilicity, water uptake, water flux, and fouling resistance among membranes prepared with different zwitterionic monomers. Membranes prepared from the copolymer with 2-methacryloyloxyethyl phosphorylcholine were the most hydrophilic and had the highest water permeance, higher than that of commercial membranes of similar pore size. Furthermore, these membranes showed unprecedented fouling resistance, exhibiting no measurable flux decline throughout a 24 h protein fouling experiment. The structure-property relationships gleaned from this survey of different zwitterion structures serves as a guideline to develop new zwitterionic materials for various applications such as membranes, drug delivery, and sensors.

Molecular Dynamics of Amphiphilic Random Copolymers in the Bulk: A 1H and 19F NMR Relaxometry Study

“…Neutral amphiphilic random copolymers were recently shown to form single‐chain folded nanoassemblies, often referred to as unimer micelles, in water solution via hydrophobic interactions among alkyl, fluoroalkyl, or siloxane side chains . Amphiphilic random copolymers were also found to phase separate in nanodomains in thin films because of the mutual chemical incompatibility between the constituent repeating units, resulting in complex structures with contrasting responses to interacting systems like proteins, cells, and organisms. However, the investigation of the self‐assembling and phase separation at the nanoscale of amphiphilic random copolymers in the bulk, which could open novel avenues to easier fabrications and applications in nanotechnologies, is still an unexplored field …”

Fully bio-based zwitterionic membranes with superior antifouling and antibacterial properties prepared via surface-initiated free-radical polymerization of poly(cysteine methacrylate)

“…These antifouling properties arise from their electrical neutrality with equivalent positively and negatively charged groups, and through a hydration layer formed by solvation of the charged groups, assisted by hydrogen bonding, which creates a physical and energetic barrier. 8 Polymers incorporating zwitterionic molecules such as phosphorylcholine, 9 sulfobetaine 10,11 and carboxybetaine 12 have been reported to be promising for anti-biofouling surfaces. However, to the best of our knowledge, relatively little work has been focused on polymers containing amino acid motifs as side chains, in particular those containing cysteine.…”

Spontaneous Self‐Assembly and Micellization of Random Copolymers in Organic Solvents

“…Supramolecular structures formed by block copolymers (BCPs) have attracted extensive attention due to their ability to create ordered structures and the wide variety of morphologies that can be achieved by manipulating block lengths and chemistries . Random copolymers (RCPs) can also form micelles and microphase separated domains, but this requires a much higher degree of incompatibility between segments and/or degree of solvent selectivity due to the close proximity and short clusters of the incompatible repeat units. When this criterion is achieved, RCPs can form an even wider range of micelle morphologies (spheres, rods, honeycombs, vesicles, etc.…”

“…[13,14] Supramolecular structures formed by block copolymers (BCPs) have attracted extensive attention due to their ability to create ordered structures and the wide variety of morphologies that can be achieved by manipulating block lengths and chemistries. [15][16][17][18][19][20][21] Random copolymers (RCPs) can also form micelles [22][23][24] and microphase separated domains, [25,26] but this requires a much www.advancedsciencenews.com www.mcp-journal.de by the entropic penalty associated with the fact that the corona segments in an RCP have to loop and re-enter the micelle, [52] and the relatively minor enthalpic gain observed in less selective solvents than water. Indeed, while BCP micelles, including crewcut micelles, have been prepared in organic solvents in previous studies, [21,[37][38][39][40][41] RCP micelles in organic solvents have not, to our knowledge, been reported.…”