Voltammetric characterisation of polyelectrolyte adsorption/transfer at the waterj1,2-DCE interface Sorina Ulmeanu, Hye Jin Lee, Hubert H. Girault * Laboratoire d'Electrochimie, D epartement de Chimie, Ecole Polytechnique F ederale de Lausanne, CH-1015 Lausanne, Switzerland Received 11 June 2001; received in revised form 6 July 2001; accepted 6 July 2001 Abstract The voltammetric characterisation of aqueous soluble polyelectrolytes at the waterj1,2-dichloroethane interface was investigated. The polyelectrolytes studied included poly diallyldimethylammonium chloride) PDADMACl) and polyethylenimine PEI). The adsorptionprocessfollowedbythetransferofthesepolyelectrolytesacrosstheinterfacewascharacterised.Theobservabletransferof the monomer cation of the PDADMA  , namely diallyldimethylammonium DADMA   ion, was compared to that of the poly- electrolyte transfer process. Physical data including the diusion coecient and the Gibbs energy of transfer across the waterj1,2- dichlorethane interface was evaluated for both the polycation and monocation. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Polyelectrolytes; Adsorption phenomenon; Ion transfer; Liquid/liquid interfaces 1. Introduction Polyelectrolytes have attracted much attention in the ®eld of polymer science particularly due to their dual character as highly charged electrolytes and ¯exible chain molecules. Interactions between polyelectrolytes and interfaces are of importance for a wide variety of biological, medical and technological processes [1]. Al- though adsorption of polyelectrolytes at solidjliquid interfaces [2±6] or airjwater interfaces have been widely studied [7±11], the adsorption of polyelectrolytes at liquidjliquid interfaces has not been as much thoroughly investigated [12]. To date, most electrochemical studies at liquidjliquid interfaces have been undertaken with two macroscopic liquid phases such as water and an organic electrolyte solution. Recently, Corn et al. [13±17], following the approach pioneered by Decher et al. [18±22], have pro- posed the use of alternate polycation and polyanion multilayers for the fabrication of ultra-thin aqueous layers, so as to support a thin aqueous phase on a solid electrode. This approach could reduce problems such as spectroscopic access, which has previously limited the use of non-surface selective spectroscopic techniques in studying the L/L interface due to the overwhelming background contribution of the bulk solution. Various aqueous polyelectrolytes have been employed to as- semble such thin multilayer ®lms such as polyL-lysine) and polyL-glutamic acid) [13], polystyrenesulfonate) PSS) and polyallylamine hydrochloride) PAH) [19]. Inordertoemploysuchpolyelectrolytesinthestudyof liquidjliquid systems, it is important to understand the transferandadsorptioncharacteristicsofpolyelectrolytes at macroscopic liquidjliquid interfaces. One of the most useful electrochemical techniques to characterise the ion transfer and adsorption processes is cyclic voltammetry, and in this paper, we shall present the voltammetric characterisationoftheadsorptionandtransferprocesses of two polyelectrolytes, polydiallyldimethylammonium chloride) PDADMACl) and polyethylenimine PEI) at the polarised waterj1,2-DCE interface. 2. Experimental PDADMACI 20% wt/wt) in water solution having M w  100; 000±200; 000 and PEI 50% wt/wt) in water solution M w  2000 were purchased from Aldrich Chemical, Bistriphenylphosphoranylidene) ammonium tetrakis4-chlorophenyl) borate BTPPATPBCl) was Electrochemistry Communications 3 2001) 539±543 www.elsevier.com/locate/elecom * Corresponding author. Tel.: +41-21-693-3151; fax: +41-21-693- 3667. E-mail address: hubert.girault@ep¯.ch H.H. Girault). 1388-2481/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S1388-248101)00209-0