Remarkable pH-sensitivity and anti-fouling property of terpolymer blended polyethersulfone hollow fiber membranes

CO2-Switchable Membranes Prepared by Immobilization of CO2-Breathing Microgels

Herein, we report the development of a novel CO₂-responsive membrane system through immobilization of CO₂-responsive microgels into commercially available microfiltration membranes using a method of dynamic adsorption. The microgels, prepared from soap-free emulsion polymerization of CO₂-responsive monomer 2-(diethylamino)ethyl methacrylate (DEA), can be reversibly expanded and shrunken upon CO₂/N₂ alternation. When incorporated into the membranes, this switching behavior was preserved and further led to transformation between microfiltration and ultrafiltration membranes, as indicated from the dramatic changes on water flux and BSA rejection results. This CO₂-regulated performance switching of membranes was caused by the changes of water transportation channel, as revealed from the dynamic water contact angle tests and SEM observation. This work represents a simple yet versatile strategy for making CO₂-responsive membranes.

Highly Porous Poly(high internal phase emulsion) Membranes with "Open-Cell" Structure and CO2-Switchable Wettability Used for Controlled Oil/Water Separation

Polymer membranes with switchable wettability have promising applications in smart separation. Hereby, we report highly porous poly(styrene-co-N,N-(diethylamino)ethyl methacrylate) (i.e., poly(St-co-DEA)) membranes with "open-cell" structure and CO₂-switchable wettability prepared from water-in-oil (W/O) high internal phase emulsion (HIPE) templates. The open-cell porous structure facilitates fluid penetration through the membranes. The combination of CO₂-switchable functionality and porous microstructure enable the membrane with CO₂-switchable wettability from hydrophobic or superoleophilic to hydrophilic or superoleophobic through CO₂ treatment in an aqueous system. This type of membrane can be used for gravity-driven CO₂-controlled oil/water separation, in which oil selectively penetrates through the membrane and separates from water. After being treated with CO₂ switching wettability of the membrane, a reversed separation of water and oil can be achieved. Such a wettability switch is fully reversible, and the membrane could be regenerated through simple removal of CO₂ and oil residual through drying. This facile and cost-effective approach represents the development of the first CO₂-switchable polyHIPE system, which is promising for smart separation in a large volume.

Graphene oxide linked sulfonate-based polyanionic nanogels as biocompatible, robust and versatile modifiers of ultrafiltration membranes

A GO linked sulfonate-based polyanionic nanogel as a membrane modifier has application potential in clinical hemodialysis and other biomedical therapies.

Surface modification of silk fibroin fabric using layer-by-layer polyelectrolyte deposition and heparin immobilization for small-diameter vascular prostheses

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

One-pot cross-linked copolymerization for the construction of robust antifouling and antibacterial composite membranes

This study reports a highly efficient, convenient and universal protocol for the fabrication of robust antifouling and antibacterial polymeric membranes via one-pot cross-linked copolymerization of functional monomers.

Efficacy of CNT-bound polyelectrolyte membrane by spray-assisted layer-by-layer (LbL) technique on water purification

This study demonstrates anti-fouling properties of surface-modified polyethersulfone composite ultrafiltration membranes prepared by a spray-assisted layer-by-layer technique.

Surface-engineered nanogel assemblies with integrated blood compatibility, cell proliferation and antibacterial property: towards multifunctional biomedical membranes

This study presents the fabrication of multifunctional nanolayers on biomedical membrane surfaces by using LBL self-assembly of nanogels and heparin-like polymers.

pH-sensitive membranes prepared with poly(methyl methacrylate) grafted poly(vinylidene fluoride) via ultraviolet irradiation-induced atom transfer radical polymerization

Ultraviolet (UV) irradiation induced atom transfer radical polymerization (ATRP) was performed to graft poly(methyl methacrylate) (PMMA) onto poly(vinylidene fluoride) (PVDF) and obtain copolymer (PVDF-g-PMMA).

Humic acid removal and easy-cleanability using temperature-responsive ZrO2 tubular membranes grafted with poly(N-isopropylacrylamide) brush chains

New poly(N-isopropylacrylamide) brushes grafted with ZrO2 (PNIPAAm-g-ZrO2) composite membranes, which had been prepared in our laboratory, were used for humic acid (HA) removal. We found that the fluxes associated with such membranes, when compared to those obtained from unmodified ZrO2 membranes, declined slightly at both 25 °C and 35 °C. The PNIPAAm-g-ZrO2 membrane achieved a high rejection, of 98.0%, at a suitable steady flux of 111.9 L m(-2) h(-1) at 25 °C. This membrane exhibited good anti-fouling properties as well as improved membrane performance during filtration of HA. The important role of pH and Ca(2+) concentration in HA removal was also investigated. Lower adsorption fouling and a higher rejection were obtained at higher pH levels. The Ca(2+) ions reduced the electrostatic exclusion and played a cross-linking role between HA and the PNIPAAm-g-ZrO2 membrane surface. Fouling was severe in the presence of Ca(2+). These tests led to the development of an environment-friendly membrane cleaning method, by means of temperature-change water elution around LCST of PNIPAAm-brushes. After the alternate temperature-change (25 °C/35 °C) cleaning, a flux recovery of 98.2% was obtained for the PNIPAAm-g-ZrO2 membrane. Moreover, after four repeated experiments, the anti-fouling and easy-cleaning properties were still maintained. It is implied that PNIPAAm-brushes were firmly "stuck" to the membrane surface, and could not easily be removed by water cleaning or HA filtration. The PNIPAAm-g-ZrO2 membranes exhibited good stability and great potential for HA removal.