Layered Polyelectrolyte Films as Selective, Ultrathin Barriers for Anion Transport

Abstract

Jeremy J. Harris, Jacqueline L. Stair, and Merlin L. Bruening, 'Layered Polyelectrolyte Films as Selective, Ultrathin Barriers for Anion Transport', Chemistry of Materials, Vol. 12 (7): 1941-1946, June 2000, doi: http://pubs.acs.org/doi/pdf/10.1021/cm0001004.Synthesis of high-flux composite membranes requires methods for deposition of ultrathin, defect-free films on highly permeable supports. Layer-by-layer deposition of polyelectrolytes on porous alumina (0.02 ??m pore diameter) produces such membranes. Electron microscopy shows that five bilayers (<25 nm) of poly(allylamine hydrochloride) (PAH)/poly(styrenesulfonate) (PSS) are sufficient to cover porous alumina and that underlying pores are not clogged during the deposition process. The selectivity of anion transport through these membranes increases with the number of bilayers until the substrate is fully covered. Fivebilayer PAH/PSS membranes have Cl-/SO4 2- and Cl-/Fe(CN)6 3- selectivity values of 7 and 310, respectively. PAH/poly(acrylic acid) membranes show selectivity values similar to those of PAH/PSS membranes but with a 3-fold decrease in anion flux. Selectivity in both of these systems likely results from Donnan exclusion

Electrochemical Characterization of a Self-Assembled Polyelectrolyte Film

“…The film permeability to ions was firstly evaluated using an electrochemical probe, [Fe(CN) 6 ] 3-/4-, and cyclic voltammetry. Two different effects can be understood from the cyclic voltammograms obtained (Fig.…”

“…The construction of a polyelectrolyte film by self-assembling is very simple and easy but, probably, the major advantage of this layer-by-layer adsorption is that many different materials can be incorporated in multilayer films, having an important contribution to the several applications of these films, from which it can be highlighted separation [6] and sensor devices [7][8][9][10][11][12][13].…”

Ion Permeability of Free-Suspended Layer-by-Layer (LbL) Films Prepared Using an Alginate Scaffold

“…The addition of a terminal PAH layer cancelled the Donnan effect, resulting in ions. Harris and coworkers also reported that Donnan exclusion played a significant role in ion transport across LbL films prepared on porous supports [33]. …”

“…LbL films composed of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS), which were deposited on the surface of porous supports (pore diameter 20-200 nm), exhibited a high flux of monovalent ions while the flux of multivalent ions was significantly suppressed as a result of enhanced Donnan exclusion, as well as hindered diffusion in the film [33][34][35]. The selective permeation of organic compounds has also been reported [31].…”

“…These results suggest that LbL films hold promise for future application to selective separator layers. Previously, LbL films were deposited on solid supports with micro-pores to study their permeability due to their fragile nature [33,34]. However, evaluation of the ion permeability of support-free LbL films would be of significant importance.…”