Controlling the Nanofiltration Properties of Multilayer Polyelectrolyte Membranes through Variation of Film Composition

Abstract

We report the use of a variety of polyelectrolyte multilayers (PEMs) as selective skins in composite membranes for nanofiltration (NF) and diffusion dialysis. Deposition of PEMs occurs through simple alternating adsorption of polycations and polyanions, and separations can be optimized by varying the constituent polyelectrolytes as well as deposition conditions. In general, the use of polycations and polyanions with lower charge densities allows separation of larger analytes. Depending on the polyelectrolytes employed, PEM membranes can remove salt from sugar solutions, separate proteins, or allow size-selective passage of specific sugars. Additionally, because of the minimal thickness of PEMs, NF pure water fluxes through these membranes typically range from 1.5 to 3 m3/(m2 day) at 4.8 bar. Specifically, to separate sugars, we employed poly(styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films, which allow 42% passage of glucose along with a 98% rejection of raffinose and a pure water flux of 2.4 m3/(m2 day). PSS/PDADMAC membranes are also capable of separating NaCl and sucrose (selectivity of approximately 10), while high-flux chitosan/hyaluronic acid membranes [pure water flux of 5 m3/(m2 day) at 4.8 bar] may prove useful in protein separations.

Microscale Enzymatic Optical Biosensors Using Mass Transport Limiting Nanofilms. 1. Fabrication and Characterization Using Glucose as a Model Analyte

“…[28][29][30] Utilizing surface adsorbed polyelectrolyte nanofilms to control substrate diffusion, a more complex microparticle biosensor system based on calcium alginate hydrogel microspheres that contained and an oxygen-quenched ruthenium compound was demonstrated. 9,24,31 In this system, which used glucose as a model analyte, local oxygen levels (internal to the particle) are proportionally reduced through glucose oxidase (GOx)-initiated catalysis (Scheme 1) and tracked through relative changes in ruthenium emission properties.…”

Intracellular delivery and sensing based on polyelectrolyte multilayer capsules

“…The capsule wall represents a semipermeable membrane, as small molecules can diffuse almost freely through the pores [13], whereas large molecules, for example dextran molecules or proteins, cannot pass the capsule walls. The molecular weight cut-off (MWCO) for PSS/PAH is around 200 Da [14]. The MWCO depends on the polymers, and…”

“…Miller and Bruening showed that, for example, the combination of hyaluronic acid (HA) and chitosan had a MWCO of ≈17,000 Da [14,15]. Due to the semipermeability of the capsule wall a Donnan equilibrium occurs [16], which means that the concentration of ions and molecules inside of the capsules is different of the concentrations outside, also in case of molecules or ions, for which the membrane is permeable.…”

Preparation of multifunctional hollow fiber nanofiltration membranes by dynamic assembly of weak polyelectrolyte multilayers

“…PEM's can provide membranes with antifouling functionalities [11,12,[14][15][16][17][18], as well as act as the separation (skin) layer for NF membranes [19]. Most of the previous studies on PEM based NF membranes, utilized flat sheet membrane supports as reported for example by Bruening et al [20][21][22][23][24][25] and Tieke et al [26,27]. However, the hollow fiber configuration would offer a higher productivity [28,29].…”