Remote Performance Modulation of Ultrafiltration Membranes by Magnetically and Thermally Responsive Polymer Chains

Abstract

Ultrafiltration membranes, that respond to an external magnetic field and local temperature have been developed. Surface-initiated activator-generated electron transfer (AGET) atom transfer radical polymerization (ATRP) has been used to graft poly(N-isopropylacrylamide) (PNIPAm) from the surface of 300 kDa regenerated cellulose membranes. The polymerization initiator was selectively attached to the entire membrane surface, only the outer membrane surface or only the inner pore surface. A superparamagnetic nanoparticle was attached to the end of the polymer chain. The DI water flux as well as the flux and rejection of bovine serum albumin were investigated in the absence and presence of a 20 and 1000 Hz oscillating magnetic field. In an oscillating magnetic field, the tethered superparamagnetic nanoparticles can cause movement of the PNIPAm chains or induce heating. A 20 Hz magnetic field maximizes movement of the chains. A 1000 Hz magnetic field leads to greater induced heating. PNIPAm displays a lower critical solution temperature at 32 °C. Heating leads to collapse of the PNIPAm chains above their Lower Critical Solution Temperature (LCST). This work highlights the versatility of selectively grafting polymer chains containing a superparamagnetic nanoparticle from specific membrane locations. Depending on the frequency of the oscillating external magnetic field, membrane properties may be tuned.

Diglycolamic Acid-Functionalized MWCNT-Augmented Polymeric Beads for Efficient Separation of Trivalent Lanthanides and Actinides

“…Although most of the spectra were consistent with those of pristine polysulfone beads due to the small DGA-CNT content, a characteristic peak for the carbonyl group (>CO) was observed at 1665 cm –1 . − Also, the peak increased with increasing load of DGA-CNTs in polysulfone. Furthermore, the −OH bending peak for carboxylic acid was also observed at 1405 cm –1 . − The observations confirm the incorporation of DGA-CNTs into the polysulfone polymeric beads. Furthermore, the highly porous nature of the PS beads was confirmed by the SEM image of pristine beads (Figure c).…”

Advanced stimuli-responsive membranes for smart separation

“…In recent years, researchers have turned to stimuli-responsive materials as a novel approach to improving membrane surface properties for reducing fouling. [227][228][229] These functional materials not only modify surface characteristics but also change morphologies in response to environmental stimuli. The self-regulated surface structure of the membranes promotes the elimination of contaminants clinging to the membrane surface and endows the membranes with self-cleaning capability.…”

Aggregate Removal by Responsive Electrospun Membrane based Hydrophobic Interaction Chromatography

“…Since the feed is pumped by convective flow through the membrane pores, pore diffusional resistances are minimized. Further membrane modules scale linearly unlike packed beds which are often difficult to scale up [22][23][24]. Numerous previous studies describe the use of membrane based HIC for protein purification [25][26][27][28][29][30][31].…”