Influence of Adsorption Conditions on the Structure of Polyelectrolyte Multilayers

Büscher, Karsten; Graf, Karlheinz; Ahrens, H.; Helm, Christiane A.

doi:10.1021/la011682m

Cited by 190 publications

(213 citation statements)

References 22 publications

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“…The influence of salt concentration and molecular mass of PEI on the interaction forces was investigated in detail. The PEI layers were adsorbed at pH 9.5-9.8 at a concentration of 200 mg/L and two different salt concentrations, in order to mimic conditions for the preparation of pre-cursor layers for multilayers [7,[26][27][28]. In the following, we shall focus on PEI layers adsorbed at high salt conditions.…”

Section: Resultsmentioning

confidence: 99%

“…The adsorption conditions of the PEI layers were chosen to mimic the PEI-precursor layer used for the preparation of polyelectrolyte multilayers [7,[26][27][28]. With respect to longrange interaction forces, we studied the charge regulation of the weak polyelectrolyte PEI layers for the first time, and examined the effect of the molecular mass.…”

Section: Introductionmentioning

confidence: 99%

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Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers

Pericet-Cámara

Papastavrou

Behrens

et al. 2006

Journal of Colloid and Interface Science

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Interaction forces between pre-adsorbed layers of branched poly(ethylene imine) (PEI) of different molecular mass were studied with the colloidal probe technique, which is based on atomic force microscopy (AFM). During approach, the long-ranged forces between the surfaces are repulsive due to overlap of diffuse layers down to distances of a few nanometers, whereby regulation of the surface charge is observed. The ionic strength dependence of the observed diffuse layer potentials can be rationalized with a surface charge of 2.3 mC/m 2 . The forces remain repulsive down to contact, likely due to electro-steric interactions between the PEI layers. These electro-steric forces have a range of a few nanometers and appear to be superposed to the force originating from the overlap of diffuse layers. During retraction of the surfaces, erratic attractive forces are observed due to molecular adhesion events (i.e., bridging adhesion). The frequency of the molecular adhesion events increases with increasing the ionic strength. The force response of the PEI segments is dominated by rubber-like extension profiles. Strong adhesion forces are observed for low molecular mass PEI at short distances directly after separation, while for high molecular mass weaker adhesion forces at larger distances are more common. The work of adhesion was estimated by integrating the retraction force profiles, and it was found to increase with the ionic strength.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers

Pericet-Cámara

Papastavrou

Behrens

et al. 2006

Journal of Colloid and Interface Science

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“…Due to the disordered structure of PEM, structural studies at this level of detail are difficult. It has, however, been proven by neutron reflectivity studies that -for suitable preparation conditions -hydrophobic interaction plays a major role in the layer-by-layer formation process [9,79]. It is therefore quite possible that hydrophilic pathways are existing in PEM, along which sites for protons are available.…”

Section: Discussion Of Pem Spectramentioning

confidence: 99%

“…The process is predominantly driven by multiple electrostatic interactions and is therefore very versatile with respect to different charged building blocks that can be employed in multilayer formation. External parameters such as salt concentration [7], pH value [8] or temperature [9] provide control of the layer thickness, which typically lies in the range of one nm per layer. Research in the field of PEM has vastly expanded in the past two decades, as there are numerous potential applications such as containers, sensors, drug delivery, etc.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Ion Conduction in Polyelectrolyte Multilayers and Complexes

Schönhoff¹,

Imre

Bhide

et al. 2010

Zeitschrift Für Physikalische Chemie

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This paper reviews the progress made in understanding of the mechanisms of ion conduction in polyelectrolyte multilayers (PEM) and polyelectrolyte complexes (PEC). The basis are experimental conductivity data obtained by impedance spectroscopy as a function of relative humidity and temperature, respectively. Mechanically stable thin films of PEM have interesting perspectives as ion conductors, however, being prepared by self-assembly, their stoichiometry and content of ionic charge carriers is unknown. Therefore PEC act as a model material with a variable stoichiometry and known ion content.Employing poly(sodium 4-styrene sulfonate) (NaPSS) and poly(diallyldimethyl ammoniumchloride) (PDADMAC), we present conductivity spectra of dried polyelectrolyte complexes of type x NaPSS · (1 − x)PDADMAC as a function of temperature and composition, respectively. The dependence of the dc conductivity is discussed along with scaling properties of the spectra. The results show that the conductivity is always determined by the sodium ions, even in PEC with an excess of PDADMAC. The ion dynamics and transport mechanisms are, however, different in PDADMAC-rich than in NaPSS-rich PEC.PEM of different polyionic compounds are investigated in dependence on relative humidity. A general law of an exponential increase of the dc conductivity with relative humidity is found. Absolute values of the conductivity and the strength of the humidity dependence are different for different polyion materials, however, they do not depend on the type of small counterion employed in layer formation. Therefore, it is concluded that in hydrated PEM, protons are the dominant charge carriers.For both PEM and PEC we show that the MIGRATION concept developed by Funke and co-workers can be used for describing the experimental spectra over wide ranges in frequency. This implies that forward-backward hopping motions of small ions play a vital role in solid polyelectrolyte materials. Apart from these potentially successful hops, localized motions of charged particles are found to influence the conductivity spectra as well.

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“…9 The adsorption properties are dependent on many factors, such as pH and ionic strength of supporting electrolyte, 10 charge density of polyelectrolytes used, 11 solvent quality 12 and temperature. 13 The characterization methods are very versatile, from ex-situ detection such as ellipsometry, 14 atomic force microscopy, 14 quartz crystal microbalance 15 and X-ray reflectivity, 16 to in-situ measurements such as streaming potential method, 17 attenuated total reflection, 18 neutron reflectivity 16 and scanning angle reflectometry. 19 Recently, liquid-liquid interfaces coated with polyelectrolyte multilayers were studied utilizing conventional electrochemical methods such as AC voltammetry and cyclic voltammetry, and the multilayers exhibited a kinetic ion transfer hindrance.…”

mentioning

confidence: 99%

Kinetic Modulation of Pulsed Chronopotentiometric Polymeric Membrane Ion Sensors by Polyelectrolyte Multilayers

Shvarev

et al. 2007

Anal. Chem.

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Polymeric membrane ion selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ionexchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion-exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity.Polymer membrane ion-selective electrodes are widely established for the reliable assessment of ion activities in complex samples and are indispensable tools in clinical analysis. Their ionselectivity is dictated by the thermodynamic ion-exchange selectivity of the polymer membrane. Recently, ion-selective membrane electrodes have started to be interrogated by pulsed chronopotentiometry. In this new technique, a discrete current pulse is imposed across an ion-selective membrane void of added ion-exchanger sites. The potential change associated with the resulting ion flux from the sample into the sensing phase can be monitored during or, at open circuit, immediately after the pulse before the membrane is regenerated under controlled potential conditions. At high sample concentrations the observed sensitivity (electrode slope) and selectivity normally agrees with that of the corresponding ion-selective electrodes interrogated at zero current. 1, 2 The imposed ion flux, however, depletes the analyte ions in the Nernst diffusion layer at a critical concentration, and very large (ca. 10-fold Nernstian) electrode slopes are observed in this concentration range. 3 The operational ion Ultra-thin films assembled from alternate adsorption of polycations and polyanions onto a charged substrate has attracted much attention in recent years due to their facile fabrication, high versatility and multi-functionality. The application of this technique has expanded into a number of areas, including biosensor surface modificat...

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Influence of Adsorption Conditions on the Structure of Polyelectrolyte Multilayers

Cited by 190 publications

References 22 publications

Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers

Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers

Mechanisms of Ion Conduction in Polyelectrolyte Multilayers and Complexes

Kinetic Modulation of Pulsed Chronopotentiometric Polymeric Membrane Ion Sensors by Polyelectrolyte Multilayers

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