Pore Assembled Multilayers of Charged Polypeptides in Microporous Membranes for Ion Separation

Abstract

In this study, highly permeable ion-selective membranes are prepared via immobilization of polyelectrolyte multilayer networks within the inner pore structure of a microporous (pore size = 0.2 microm) support. Electrostatic layer-by-layer assembly is achieved through alternate adsorption of cationic and anionic polyelectrolytes under convective flow conditions. To initiate pore assembly, the first layer consists of covalently bound charged polypeptides (poly(L-glutamic acid) (PLGA) or poly(L-lysine) (PLL)) establishing a charged support for subsequent adsorption. Nonstoichiometric immobilization of charged multilayers within a confined pore geometry leads to an enhanced volume density of ionizable groups in the membrane phase. This overall increase in the effective charge density allows for Donnan exclusion of ionic species (especially divalent co-ions) using microporous materials characterized by permeability values that exceed conventional membrane processes. Multilayer assemblies are fabricated using both PLGA/PLL and synthetic polyelectrolytes (poly(styrenesulfonate)/poly(allylamine)) in an attempt to compare the level of adsorption and separation properties of the resulting materials. The role of salt concentration in the carrier solvent on overall polyelectrolyte adsorption was examined to determine its effect on both solute (Cl-, SO4(2-), As(V)) and water transport. Constriction of the pore size induced by multilayer propagation was monitored through permeability measurements and dextran rejection studies at each stage of the deposition process.

Enhanced electrostatic modulation of ionic diffusion through carbon nanotube membranes by diazonium grafting chemistry

“…Transport processes modulated by electro-statics are central to several separation processes including charged based nano-filtration [1], adsorption [2], ion-exchange [3] and electro osmosis [4]. Interest is also in ionic transport through pores with dimensions close to the Debye screening length which causes overlap of the electrical double layer.…”

Surface viscoelastic properties of floating polyelectrolyte multilayers films: A capillary wave study

“…Such systems have an obvious practical value, but they are also of great fundamental interest because of the properties of confined complex molecules, such as polyelectrolytes, which can be very different from their properties in the bulk [4]. To better understand and control the PEM formation, various properties of these systems, such as the effect of salt, pH, aggregation homogeneity, roughness, stability, and permeability [5][6][7][8][9][10][11], have been investigated. However, for many applications, especially when the film is deformed by shearing or for contact * Corresponding author.…”

Advanced Polymeric and Organic–Inorganic Membranes for Pressure-Driven Processes

“…They can work then as scaffolds with selective gates on the pores if surface-bound molecules that change conformation with pH are further attached to the silanes functionalities [89,90].…”