Preparation of protein-adsorption-resistant polyethersulfone ultrafiltration membranes through surface segregation of amphiphilic comb copolymer

Surface Segregation Methods toward Molecular Separation Membranes

As a highly promising approach to solving the issues of energy and environment, membrane technology has gained increasing attention in various fields including water treatment, liquid separations, and gas separations, owing to its high energy efficiency and eco-friendliness. Surface segregation, a phenomenon widely found in nature, exhibits irreplaceable advantages in membrane fabrication since it is an in situ method for synchronous modification of membrane and pore surfaces during the membrane forming process. Meanwhile, combined with the development of synthesis chemistry and nanomaterial, the group has developed surface segregation as a versatile membrane fabrication method using diverse surface segregation agents. In this review, the recent breakthroughs in surface segregation methods and their applications in membrane fabrication are first briefly introduced. Then, the surface segregation phenomena and the classification of surface segregation agents are discussed. As the major part of this review, the authors focus on surface segregation methods including free surface segregation, forced surface segregation, synergistic surface segregation, and reaction-enhanced surface segregation. The strategies for regulating the physical and chemical microenvironments of membrane and pore surfaces through the surface segregation method are emphasized. The representative applications of surface segregation membranes are presented. Finally, the current challenges and future perspectives are highlighted.

Advancements in modification of membrane materials over membrane separation for biomedical applications-Review

A comprehensive overview of various modifications carried out on polymeric membranes for biomedical applications has been presented in this review paper. In particular, different methods of carrying out these modifications have been discussed. The uniqueness of the review lies in the sense that it discusses the surface modification techniques traversing the timeline from traditionally well-established technologies to emerging new techniques, thus giving an intuitive understanding of the evolution of surface modification techniques over time. A critical comparison of the advantages and pitfalls of commonly used traditional and emerging surface modification techniques have been discussed. The paper also highlights the tuning of specific properties of polymeric membranes that are critical for their increased applications in the biomedical industry specifically in drug delivery, along with current challenges faced and where the future potential of research in the field of surface modification of membranes.

Antibiofouling Performance by Polyethersulfone Membranes Cast with Oxidized Multiwalled Carbon Nanotubes and Arabic Gum

Despite extensive research efforts focusing on tackling membrane biofouling, one of the biggest problems associated with membrane technology, there has been little headway in this area. This study presents novel polyethersulfone (PES) membranes synthesized via a phase inversion method at incremental loadings of functionalized oxidized multiwalled carbon nanotubes (OMWCNT) along with 1 wt. % arabic gum (AG). The synthesized OMWCNT were examined using scanning electron microscopy and transmission electron microscopy for morphological changes compared to the commercially obtained carbon nanotubes. Additionally energy-dispersive X-ray spectroscopy was carried out on the raw and OMWCNT materials, indicating an almost 2-fold increase in oxygen content in the latter sample. The cast PES/OMWCNT membranes were extensively characterized, and underwent a series of performance testing using bovine serum albumin solution for fouling tests and model Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial species for anti-biofouling experiments. Results indicated that the composite PES membranes, which incorporated the OMWCNT and AG, possessed significantly stronger hydrophilicity and negative surface charge as evidenced by water contact angle and zeta potential data, respectively, when compared to plain PES membranes. Furthermore atomic force microscopy analysis showed that the PES/OMWCNT membranes exhibited significantly lower surface roughness values. Together, these membrane surface features were held responsible for the anti-adhesive nature of the hybrid membranes seen during biofouling tests. Importantly, the prepared membranes were able to inhibit bacterial colonization upon incubation with both Gram-positive and Gram-negative bacterial suspensions. The PES/OMWCNT membranes also presented more resilient normalized flux values when compared to neat PES and commercial membrane samples during filtration of both bacterial suspensions and real treated sewage effluents. Taken together, the results of this study allude to OMWCNT and AG as promising additives, for incorporation into polymeric membranes to enhance biofouling resistance.

The effect of chain architecture on the phase behavior of A4B4 miktoarm block copolymers

Well-defined miktoarm (polystyrene)₄-(polylactic acid)₄ ((PS)₄-(PLA)₄) block copolymers were synthesized and their phase behaviors were compared with linear PS-b-PLA block copolymers, in which the miktoarm architecture enhanced the phase segregation.

Effect of volatile solvent and evaporation time on formation and performance of PVC/PVC-g-PEGMA blended membranes

The synthesis process of the PVC/PVC-g-PEGMA membranes.

Zwitterionic materials for antifouling membrane surface construction

Membrane separation processes are often perplexed by severe and ubiquitous membrane fouling. Zwitterionic materials, keeping electric neutrality with equivalent positive and negative charged groups, are well known for their superior antifouling properties and have been broadly utilized to construct antifouling surfaces for medical devices, biosensors and marine coatings applications. In recent years, zwitterionic materials have been more and more frequently utilized for constructing antifouling membrane surfaces. In this review, the antifouling mechanisms of zwitterionic materials as well as their biomimetic prototypes in cell membranes will be discussed, followed by the survey of common approaches to incorporate zwitterionic materials onto membrane surfaces including surface grafting, surface segregation, biomimetic adhesion, surface coating and so on. The potential applications of these antifouling membranes are also embedded. Finally, we will present a brief perspective on the future development of zwitterionic materials modified antifouling membranes.

STATEMENT OF SIGNIFICANCE

Membrane fouling is a severe problem hampering the application of membrane separation technology. The properties of membrane surfaces play a critical role in membrane fouling and antifouling behavior/performance. Antifouling membrane surface construction has evolved as a hot research issue for the development of membrane processes. Zwitterionic modification of membrane surfaces has been recognized as an effective strategy to resist membrane fouling. This review summarizes the antifouling mechanisms of zwitterionic materials inspired by cell membranes as well as the popular approaches to incorporate them onto membrane surfaces. It can help form a comprehensive knowledge about the principles and methods of modifying membrane surfaces with zwitterionic materials. Finally, we propose the possible future research directions of zwitterionic materials modified antifouling membranes.

PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers—ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)—is presented.

Ultralow Oil-Fouling Heterogeneous Poly(ether sulfone) Ultrafiltration Membrane via Blending with Novel Amphiphilic Fluorinated Gradient Copolymers

A novel amphiphilic fluorinated gradient copolymer was prepared by semibatch reversible addition-fragmentation chain transfer (RAFT) method using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate (TFOA) as monomers. The resultant amphiphilic copolymers were then incorporated into the poly(ether sulfone) (PES) to fabricate PES blend membranes via the non-solvent-induced phase separation method (NIPS). During the phase inversion process, both hydrophilic (PEGMA) and low surface energy (TFOA) segments significantly enriched on the membrane surface by surface segregation to form an amphiphilic surface, which was demonstrated by surface wetting properties and X-ray photoelectron spectroscopy (XPS) measurements. According to the filtration experiments of oil-in-water emulsion, the heterogeneous membranes exhibited superior oil-fouling resistant properties, that is, low flux decay (as low as 15.4%) and high flux recovery (almost 100%), compared to the pure PES membrane. The synergistic effect of fouling-resistant and fouling-release mechanisms was found to be responsible for the excellent antifouling capacities. The findings of this study offer a facile and robust strategy for fabricating ultralow oil-fouling membranes that might be used for effective oil/water separation.

Preparation of a novel thermo responsive PSF membrane, with cross linked PVCL-co-PSF copolymer for protein separation and easy cleaning

An amphiphilic thermo responsive PVCL-co-PSF copolymer was synthesized with enhanced pore density and hydrophilicity. It was found to have high hydration capacity and low BSA adsorption, with 92.5% and 95% flux recovery ratios achieved for BSA and HA, respectively.

From commodity polymers to functional polymers

Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications.

Isotherm and kinetic behavior of adsorption of anion polyacrylamide (APAM) from aqueous solution using two kinds of PVDF UF membranes

To determine the isotherm parameters and kinetic parameters of adsorption of anion polyacrylamide (APAM) from aqueous solution on PVDF ultrafiltration membrane (PM) and modified PVDF ultrafiltration membrane (MPM) is important in understanding the adsorption mechanism of ultrafiltration processes. Effect of variables including adsorption time, initial solution concentration, and temperature were investigated. The Redlich-Peterson equation of the five different isotherm models we chose was the most fitted model, and the R(2) was 0.9487, 0.9765 for PM and MPM, respectively; while, the pseudo-first-order model was the best choice among all the four kinetic models to describe the adsorption behavior of APAM onto membranes, suggesting that the adsorption mechanism was a chemical and physical combined adsorption on heterogeneous surface. The thermodynamic parameters were also calculated from the temperature dependence (Δ(r)G(m)(θ), Δ(r)H(m)(θ), Δ(r)S(m)(θ)), which showed that the process of adsorption is not spontaneous but endothermic process and high temperature favors the adsorption.

Protein fouling resistant membrane prepared by amphiphilic pegylated polyethersulfone

A mild and facile grafting of poly(ether glycol) methyl ether methacrylate (PEGMA) monomers onto polyethersulfone (PES) was carried out. Then, the PES-g-PEGMA membranes with integrally anisotropic morphology were fabricated through the coupling of non-solvent induced phase inversion and surface segregation. Compared with PES control membrane, the surface hydrophilicity of PES-g-PEGMA membranes was remarkably enhanced due to the drastic enrichment of poly(ethylene glycol) (PEG) segments on the membrane surface; protein adsorption was significantly inhibited due to the hydrogen bonding interactions between hydrophilic groups and water molecules. Ultrafiltration experiments were used to assess the permeability and protein fouling resistance of the PES-g-PEGMA membranes. It was found that the PES-g-PEGMA membranes with higher surface coverage of PEG segments displayed stronger antibiofouling property. Moreover, the stable antibiofouling property for PES-g-PEGMA membranes was acquired due to covalent bonding interactions between hydrophilic PEGMA side chains and PES main chains.