Dynamic pressure‐driven covalent assembly of inner skin hollow fiber multilayer membrane

Abstract

A covalent assembly was accomplished onto hollow fibers via a dynamic pressuredriven layer-by-layer (LbL) technique. The covalent crosslinking multilayers were successfully formed onto the inner surfaces of hollow fiber porous substrates during the alternatively filtration of polyethyleneimine (PEI) and glutaraldehyde (GA) solutions. The formation of covalent bond between PEI and GA was confirmed using fourier transform infrared (FTIR) spectra. The thickness increment on a quartz slide clearly suggested the stepwise growth of multilayer at nanometer scale. The regular alternation of zeta potentials demonstrated that the successful formation of GA-crosslinked PEI multilayers on the hollow fibers. The multilayer membranes showed excellent pervaporation performances for the dehydration of different solvent-water mixtures. The selectivity and permeability can be controlled by varying the PEI layer number. More importantly, the covalent assembled multilayer membrane rendered much higher stabilities compared with those from electrostatically LbL assembly, which offers much opportunity for practical applications.

Highly crosslinked layer-by-layer polyelectrolyte FO membranes: Understanding effects of salt concentration and deposition time on FO performance

“…This technique can be applied for many porous membrane substrates with different sizes and topology that can adsorb the initial polyelectrolyte layer such as poly(ether sulfone), poly(vinylamine), poly(4-methyl-1-pentene), polyamide, polyacrylonitrile (PAN), poly(vinyl pyrrolidone), anodic alumina in flat sheet, tubular [32] or hollow fiber [33] structures. Previous studies proved that the LbL formation mostly depended on the polyelectrolytes and adsorption conditions than the substrate [28].…”

Universal surface modification by aldehydes on polymeric membranes for isopropanol dehydration via pervaporation

“…The HPEI pre-treatment would not only introduce abundant primary amino groups on the membrane surface for the subsequent aldehyde modification but also improve the overall hydrophilicity as well as effectively seal the membrane defects [27][28][29][30]. A covalent assembly of HPEI-glutaraldehyde multilayer on hydrolyzed polyacrylonitrile HF membranes had been fabricated by the layer-by-layer method for alcohol dehydration [31], but this method needed vacuum assistance during assembly and involved multiple steps including washing and drying after each assembly, which might incur additional costs and prolong production duration. Since the HPEI mediated aldehyde modification method (including HPEI pretreatment and then aldehyde modification) can be easily extended to other polymeric membranes such as Ultem s , PES and others; this study may provide useful insights of using aldehydes to design next generation membranes for pervaporation applications.…”

Rapid assembly of polyelectrolyte multilayer membranes using an automatic spray system

“…Therefore, it is very important to understand the variations of substrate surface charge properties after alternately spraying polycation and polyanion solutions. Measurement of the zeta potential has been demonstrated to be a useful approach to monitor the stepwise growth of sequential polymer layers during the LbL assembly process . The surface zeta potential was tracked using an electrokinetic analyzer before and after spraying polyelectrolyte layer on to the flat sheet porous polymeric substrate.…”

“…In fact, our group has been committed to the simplification of the LbL procedure for a long time. For example, we utilized a dynamic LbL process to prepare polyelectrolyte multilayers on both flat‐sheet and hollow fiber UF membranes, which significantly reduced the deposition cycles while retaining good pervaporation properties . Lee and coworkers have developed the LbL assembly of a poly(((4,4′‐bis(6‐dimethylammonio)hexyl)‐oxy)azobenzene bromide) (PAZ‐6) and carrageenan multilayer by using a spin‐coating method .…”