Polyelectrolyte deposition

We used polyelectrolyte multilayer formed from polyallylamine hydrochloride (PAH) and PSS successfully for templating deposition of colloidal particles, as displayed in Fig. 12. The wavelength of the wrinkles was adjusted by the number of polyelectrolyte deposition cycles and, accordingly, single lines of particles or double lines, as well as other geometries, could be achieved [70],... 

Fig. 11 (a) Optical microscopy images of the release from ibuprofen crystals covered with a (CHI/dextran sulfate)is shell 1 before dissolution 2 during dissolution and 3 after removal of the crystal cores. The mean size of the encapsulated ibuprofen microcrystals is 15.3 am. Reproduced from [112]. (b) Fluorescence increases with time, obtained by dissolving fluorescein crystals covered with shells of different thicknesses (9, 13, 15, and 18 polyelectrolyte-deposited PSS/PAH layers). The release from the native (uncovered) fluorescein crystals is shown as 0. Reproduced from [122]... 

Roberts MJ (1999) Nonlinear optical film formed layer-by-layer using alternating polyelectrolyte deposition. In Organic thin films for photonics applications. Optical Society of America, Washington DC, p 38... 

E. Donath, A. Sukhomkov, F. Caruso, S. Davies, and H. Mohwald, Microcapsules from layer-by-layer polyelectrolyte deposition, Angew. Chem. Int. Ed. 37, 2201-2205 (1998). 

Electrokinetic measurements for the polyelectrolyte layers were carried out by means of an Electrokinetic Analyzer device (A. Paar KG, Austria). The glass substrate after polyelectrolyte deposition was several times rinsed with deionized water to ensure that unadsorbed polymers do not contribute to the f -potential measured. The values of -potential were calculated according to the formula ... 

Fig. 7 Effect of graft yield and polyelectrolyte deposition on the irreversible fouling of PP membranes with Human-Serum-Albumin (HSA) (pH 6.5)...

Ringenbach E, Chauveteau G, Pefferkorn E. Polyelectrolyte deposition induced by ion complexation structural and electrochemical characteristics of the polymeric interface. J Colloid Interface Sci 1995 171 218-223. 

We present the observation of a distance-dependent enhancement and quenching of semiconductor nanocrystal photoluminescence near gold colloids. A layer-by-layer polyelectrolyte deposition technique was used for varying the distance between gold nanoparticles and quantum dots. The maximum enhancement by a factor of five is achieved for a 9-layer spacer (11 nm). 

Very recently Bawendi and co-workers [4] reported about fivefold increase in the observed fluorescence intensity of single CdSe/ZnS nanocrystalls (NCs) and striking reduction in their fluorescence blinking behavior due to interactions with a rough metal film. The distance-dependent enhancement and quenching of NC fluorescence has been observed by us using the layer-by-layer polyelectrolyte deposition technique to insert well-defined spacer between gold colloidal films and NCs [5] with maximum enhancement for the 9-layer spacer ( 11 nm in thickness). 

A.L. Morales-Cruz, E.R. Fachini, F.A. Miranda, and C.R. Cabrera, Surface analysis monitoring of polyelectrolyte deposition on Bao.sSro.sTiOs thin films, App. Surface ScL, 253,8846-8857 (2007). 

In addition, dual layer hollow fibers have been manufactured by a dry jet-wet spinning technique [81]. Two different polymers, i.e., PAI and poly(ether sul-fone), were used as the selective layer on the outer side and the porous support layer on the inner side, respectively. The dual layer substrates were subsequently modified crosslinking followed by multilayer polyelectrolyte depositions in order to get a nanofiltration skin on the outer layer. 

Studies with silane-modified latexes suggest that low molecular weight, water-soluble polyelectrolytes deposit preferentially on a mineral surface to give a well-ordered layer of modifier between the latex polymer and the mineral surface. Physical... 

Control of the permeability of LPFs will play a crucial role in their possible application as sensor materials or protective coatings. The earlier-mentioned experiments show that it is possible to prepare LPFs with a variety of permeabilities. Constituent polyelectrolytes, deposition conditions, and postdeposition treatments can all be chosen to tailor a film for specific needs. 

This chapter deals primarily with monolayers of surfactants at fluid interfaces, but some attention is also given to (nano) coatings such as Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films, self-assembled monolayers (SAMs), and layers obtained by alternating polyelectrolyte deposition. Such coatings may be applied for the functionalization of surfaces, for instance, to achieve biocompatibility of biomaterials, improve specificity and selectivity of biosensors and membranes, and control immobilization of enzymes or cells in bioreactors. 

Figure 3.1 Schematic illustration of the polyelectrolyte deposition process and of subsequent core decomposition.

Studies on PEM are of interest because of the versatility of multilayer formation process with respect to variety of support materials, combination with other assembly techniques and possibility of incorporation of different functional species [1-4]. PEM are applied in chemical and biochemical sensing or preparation of new biomaterials. When colloidal particles or emulsion droplets are used as cores for polyelectrolyte deposition one can obtain hollow micro- and nanocapsules. Such capsules have potential as drug delivery systems [5] capable of sustained release [6,7], microreactors [8,9] or catalytic systems [8-10]. Detailed summaries on the properties and application of PEM prepared by LbL technique can be found in [1,11]. 

Silicon blocks (Siliciumbearbeitung Andrea Holm, Tann/ Ndb., Germany) of dimensions 80 x 50 x 15 mm and orientation (100) with two sides polished were used as supports for polyelectrolyte deposition in the neutron reflectometry experiments. The blocks were cleaned with piranha solution (H2SO4/H2O2I 1). Caution - The piranha solution is strong oxidizing agent and should be handled carefully) for 30 min and carefully rinsed with distilled water. Finally, the Si substrates were dipped for 30 min in hot water (ca. 70 °C). 

The dye used in this work was alizarin violet. PAH (MW = 70 000) and the dye was purchased from Aldrich Chemical Co. and PAA (MW = 90 000) was obtained from Polyscience as 25 % aqueous solution. All the chemicals were used without further purification. The chemical structure of alizarin violet is shown in Fig. 1. The polyelectrolyte deposition baths were prepared with 10 M (based on repeat units) aqueous solutions using 18.2 MQ Millipore water. The solutions of alizarin violet and PAH were mixed in a controlled way so that SOj ions of alizarin violet get attached to NH ions of PAH. The low concentration of alizarin in PAH allowed 80 % of the NH ions of PAH to take part in the adsorption process during layer-by-layer deposition. Use of organic molecule alone as anion generally results in material loss during washing [9, 10]. 

UVA s absorption spectroscopy was used to monitor the electrostatic self-assembly of the oiganometallic polyions. The increase in absorption at X x=216nm as a function of the number of bilayers deposited on quartz shdes is shown in Figure 3. An essentially linear dependence was found, with possibly a shght decrease in the amount of polyelectrolyte depositing per cycle as the munber of bilayers approaches 20, but overall giving evidence for a well-defined deposition process. ... 

Dauginet, L., Duwez, A.-S., Demoustier-Champagne, R.L.S. Surface modification of polycarbonate and poly(ethylene terephthalate) films and membranes by polyelectrolyte deposition. Langmuir 17, 3952-3957 (2001)... 

The random site surface (RSS) regime is pertinent to nanoparticle (colloids, proteins, polyelectrolytes) deposition at surfaces bearing isolated centers such as ions, smaller particles or macromolecules able to bind the solute particles irreversibly. 

Dynamic deposition method is also energy and time consuming in comparison to other two methods. At the cnrrent stage, dynamic deposition method using polyelectrolytes is still not snitable to be regarded as the best technique to improve the membrane surface hydrophilicity. In brief, it can be postulated that the membrane final contact angle values are strongly dependent on the type of polyelectrolyte deposited. 

Reproducibility of the deposition of polyeleetrolytes onto membranes should be improved to reduce the deviations in the data. In most cases, the performance reproducibility of the double-sided polyelectrolyte deposition method is a bit low and should be improved in comparison to the single-sided method to make it commercially feasible. This has been explained by the morphology of the membrane support materials, poorly controlled thickness of the support, unknown factors affecting the membrane support during the hydrolyzation process, and so forth. 

Active selective layer of the composite membrane can be developed by several techniques, such as interfacial polymerization, multilayer polyelectrolyte deposition, chemical cross-linking, dual layer co-extrusion/co-casting, dip-coating and UV-photo-grafting, and plasma. 

Polyelectrolyte is described as a polymer carrying (an) electrolyte(s) group in its repeating units. Polyelectrolyte presents charge property when it dissociates in water or an aqueous solution. The technique of multilayer polyelectrolyte deposition on membrane siu faces is based on the electrostatic interaction of oppositely charged molecules. A polyelectrolyte membrane can be fabricated by sequential deposition of aqueous polyelectrolyte solutions on a porous substrate, as illustrated in Figure 15.22 [115]. 

FIGURE 15.22 Schematic drawing of multilayer polyelectrolyte deposition on the outer surface of the hollow-fiber membrane. (Adapted from C. Liu et al., Desalination, 308,147-153, 2013.)... 

G. Liu, D.M. Dotzauer, M.L. Bruening, Ion-exchange membranes prepared using layer-by-layer polyelectrolyte deposition, Journal of Membrane Science, 354 (2010)... 

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