International Center for Frontier Research in Chemistry

Strasbourg, France

International Center for Frontier Research in Chemistry

Strasbourg, France
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Tirado P.,University of Strasbourg | Reisch A.,University of Strasbourg | Reisch A.,International Center for Frontier Research in Chemistry | Roger E.,University of Strasbourg | And 7 more authors.
Advanced Functional Materials | Year: 2013

Novel biochemically active compact polyelectrolyte complexes (CoPECs) are obtained through a simple coprecipitation and compaction procedure. As shown for the system composed of poly(acrylic acid) (PAA) and poly(allylamine) (PAH) as polyelectrolytes and alkaline phosphatase (ALP) as enzyme, the enzyme can be firmly immobilized into these materials. The ALP not only remains active in these materials, but the matrix also enhances the specific activity of the enzyme while protecting it from deactivation at higher temperature. The presence of the matrix allows fine control and substantial enhancement of reaction rates by varying the salt concentration of the contacting solution or temperature. The excellent reusability, together with the ease of co-immobilizing other useful components, such as magnetic particles, allowing facile handling of the CoPECs, makes these materials interesting candidates for variable scaffolds for the immobilization of enzymes for small- and large-scale enzyme-catalyzed processes. Alkaline phosphatase (ALP) is immobilized in compact polyelectrolyte complexes (CoPECs). The materials obtained in this way retain the biocatalytic activity of the enzyme, protect it from elevated temperature, and allow its fine tuning by salt concentration and temperature. Co-immobilization of magnetic particles yields easily handleable magnetic materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Schaaf P.,Charles Sadron Institute | Schaaf P.,University of Strasbourg | Schaaf P.,International Center for Frontier Research in Chemistry | Voegel J.-C.,French Institute of Health and Medical Research | And 6 more authors.
Advanced Materials | Year: 2012

The alternate deposition of polyanions and polycations on a solid substrate leads to the formation of nanometer to micrometer films called Polyelectrolyte Multilayers. This step-by-step construction of organic films constitutes a method of choice to functionalize surfaces with applications ranging from optical to bioactive coatings. The method was originally developed by dipping the substrate in the different polyelectrolyte solutions. Recent advances show that spraying the polyelectrolyte solutions onto the substrate represents an appealing alternative to dipping because it is much faster and easier to adapt at an industrial level. Multilayer deposition by spraying is thus greatly gaining in interest. Here we review the current literature on this deposition method. After a brief history of polyelectrolyte multilayers to place the spraying method in its context, we review the fundamental issues that have been addresses so far. We then give an overview the different fields where the method has been applied. Design of nanometer to micrometer thin films by spraying solutions of polyelectrolyte is a recent emerging concept in the field of surface coating. Herein the origin of this new process, the fundamental issues, and the resulting potential applications relative to spray assisted deposition from the current literature are reviewed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cini N.,Technical University of Istanbul | Tulun T.,Technical University of Istanbul | Blanck C.,Charles Sadron Institute | Toniazzo V.,CRP Henri Tudor | And 5 more authors.
Physical Chemistry Chemical Physics | Year: 2012

Polyelectrolyte "complexes" have been studied for almost a century and find more and more applications in cosmetics and DNA transfection. Most of the available studies focused on the thermodynamic aspects of the "complex" formation, mainly to determine phase diagrams and the influence of diverse physicochemical aspects on the formation of "complexes", but conversely less effort has been given to the kinetics of such processes. We describe herein the "complexation" kinetics of a short linear sodium polyphosphate (PSP) with poly(allylamine hydrochloride) (PAH) in the presence of 10 mM, 0.15 M and 1 M NaCl. We find, by using a combination of physicochemical techniques, that mixtures containing a 1 to 1 molar ratio of phosphate and amino groups allow the formation of "complexes" having a few 100 nm in diameter which progressively grow to particles up to 1.5 microns in hydrodynamic diameter, the growth process being accompanied by some progressive sedimentation. During this slow aggregation kinetics, the polyelectrolytes undergo a release of counterions and the zeta potential changes from a positive value to a negative one of -20 mV which is close to the zeta potential of (PSP-PAH) n films deposited under identical physicochemical conditions. Even though the complexes have a negative electrophoretic mobility, they contain an equimolar amount of amino and phosphate groups. This allows us to make some assumption about the structure of such "complexes" and to compare them with other published structures. We will also compare them with the aggregates found during the "layer-by-layer" deposition of the same species under the same conditions. © 2012 The Owner Societies.

De Saint-Aubin C.,CNRS Mulhouse Institute of Materials Science | Hemmerle J.,French Institute of Health and Medical Research | Boulmedais F.,Charles Sadron Institute | Boulmedais F.,International Center for Frontier Research in Chemistry | And 4 more authors.
Langmuir | Year: 2012

Although never emphasized and increasingly used in organic electronics, PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) layer-by-layer (lbl) film construction violates the alternation of polyanion and polycation rule stated as a prerequisit for a step-by-step film buildup. To demonstrate that this alternation is not always necessary, we studied the step-by-step construction of films using a single solution containing polycation/polyanion complexes. We investigated four different systems: PEDOT-PSS, bPEI-PSS (branched poly(ethylene imine)-poly(sodium 4-styrene sulfonate)), PDADMA-PSS (poly(diallyl dimethyl ammonium)-PSS), and PAH-PSS (poly(allylamine hydrochloride)-PSS). The film buildup obtained by spin-coating or dipping-and-drying process was monitored by ellipsometry, UV-vis-NIR spectrophotometry, and quartz-crystal microbalance. The surface morphology of the films was characterized by atomic force microscopy in tapping mode. After an initial transient regime, the different films have a linear buildup with the number of deposition steps. It appears that, when the particles composed of polyanion-polycation complex and complex aggregates in solution are more or less liquid (case of PEDOT-PSS and bPEI-PSS), our method leads to smooth films (roughness on the order of 1-2 nm). On the other hand, when these complexes are more or less solid particles (case of PDADMA-PSS and PAH-PSS), the resulting films are much rougher (typically 10 nm). Polycation/polyanion molar ratios in monomer unit of the liquid, rinsing, and drying steps are key parameters governing the film buildup process with an optimal polycation/polyanion molar ratio leading to the fastest film growth. This new and general lbl method, designated as 2-in-1 method, allows obtaining regular and controlled film buildup with a single liquid containing polyelectrolyte complexes and opens a new route for surface functionalization with polyelectrolytes. © 2012 American Chemical Society.

Merindol R.,Charles Sadron Institute | Merindol R.,University of Strasbourg | Diabang S.,Charles Sadron Institute | Felix O.,Charles Sadron Institute | And 6 more authors.
ACS Nano | Year: 2015

Nanocomposite films possessing multiple interesting properties (mechanical strength, optical transparency, self-healing, and partial biodegradability) are discussed. We used Layer-by-Layer assembly to prepare micron thick wood-inspired films from anionic nanofibrillated cellulose and cationic poly(vinyl amine). The film growth was carried out at different pH values to obtain films of different chemical composition, whereby, and as expected, higher pH values led to a higher polycation content and also to 6 times higher film growth increments (from 9 to 55 nm per layer pair). In the pH range from 8 to 11, micron thick and optically transparent LbL films are obtained by automated dipping when dried regularly in a stream of air. Films with a size of 10 cm2 or more can be peeled from flat surfaces; they show tensile strengths up to about 250 MPa and Young's moduli up to about 18 GPa as controlled by the polycation/polyanion ratio of the film. Experiments at different humidities revealed the plasticizing effect of water in the films and allowed reversible switching of their mechanical properties. Whereas dry films are strong and brittle (Young's modulus: 16 GPa, strain at break: 1.7%), wet films are soft and ductile (Young's modulus: 0.1 GPa, strain at break: 49%). Wet film surfaces even amalgamate upon contact to yield mechanically stable junctions. We attribute the switchability of the mechanical properties and the propensity for self-repair to changes in the polycation mobility that are brought about by the plastifying effect of water. © 2015 American Chemical Society.

Gill R.,Charles Sadron Institute | Gill R.,Quaid-i-Azam University | Gill R.,Fatima Jinnah Women University | Mazhar M.,Quaid-i-Azam University | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2010

Catching the end groups: A simple procedure was used for the covalent layer-by-layer assembly of homobifunctional H2N-poly(dimethoxysilane)-NH2 on SiO2 surfaces that leads to robust layer-by-layer films of optical quality (see picture; photo on left) despite the use of non-purified commercial starting materials. The films show a solvent memory for swelling and de-swelling when immersed in the corresponding solvent for each polymer. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cini N.,Charles Sadron Institute | Cini N.,Technical University of Istanbul | Tulun T.,Technical University of Istanbul | Decher G.,Charles Sadron Institute | And 4 more authors.
Journal of the American Chemical Society | Year: 2010

Because of its versatility, the layer-by-layer (LBL) assembly method has become a popular tool for preparing multimaterial films, yet astonishingly little is known about the fundamental rules governing their deposition. Here we show an unusual case of self-patterning LBL films made from poly(allylamine hydrochloride) and poly(sodium phosphate). In such films, both the film thickness and the film roughness increase linearly with the number of deposition steps up to a thickness of ∼ 60 nm. Even more surprising is the fact that the adsorption of individual "layers" of polyanions and polycations proceeds without a regular inversion of the - potential and with the occurrence of a growth instability at ∼ 75 layers. These findings underline the need to reconsider the fundamentals of polyelectrolyte multilayer film deposition. © 2010 American Chemical Society.

Kekicheff P.,Charles Sadron Institute | Schneider G.F.,Charles Sadron Institute | Schneider G.F.,Technical University of Delft | Decher G.,Charles Sadron Institute | And 2 more authors.
Langmuir | Year: 2013

Polyelectrolyte multilayers composed of poly(allylamine hydrochloride) and poly(styrene sulfonate) were assembled on 13 nm gold nanoparticles and characterized by Transmission Electron Microscopy and Atomic Force Microscopy. The direct measurement of the interactions at the molecular level using a Surface Force Apparatus revealed that the colloidal stability of such coated particles in aqueous media is brought about concomitantly by electrostatic and steric repulsive interactions. The cyanide induced dissolution of the gold cores yields either hollow nanocapsules or collapsed nanospheres, two species which are very difficult to distinguish. In contrast to the established micron sized hollow capsules, the dissolution of the nanosized gold cores may induce a substantial swelling of the polyelectrolyte complex into the central void as induced by the temporary local increase of the ionic strength. At least three layer pairs are required to maintain the structural integrity of the polyelectrolyte shells to yield hollow nanospheres. At about three layer pairs, thin nanocapsules are mechanically compressible and may collapse on themselves following mechanical stimulation to form even smaller spherical polyelectrolyte complex particles that retain the small polydispersity of the gold cores. Thus, the templating of polyelectrolyte shells around, e.g., gold nanoparticles followed by the dissolution of the respective cores constitutes a new method for the synthesis of extremely small polyelectrolyte complex particles with very low polydispersity. © 2013 American Chemical Society.

Qureshi S.S.,Charles Sadron Institute | Qureshi S.S.,Quaid-i-Azam University | Qureshi S.S.,Government of Pakistan | Zheng Z.,Charles Sadron Institute | And 6 more authors.
ACS Nano | Year: 2013

Layer-by-Layer (LbL) assembled films offer many interesting applications (e.g., in the field of nanoplasmonics), but are often mechanically feeble. The preparation of nanoprotective films of an oligomeric novolac epoxy resin with poly(ethyleneimine) using covalent LbL-assembly is described. The film growth is linear, and the thickness increment per layer pair is easily controlled by varying the polymer concentration and/or the adsorption times. The abrasion resistance of such cross-linked films was tested using a conventional rubbing machine and found to be greatly enhanced in comparison to that of classic LbL-films that are mostly assembled through electrostatic interactions. These robust LbL-films are then used to mechanically protect LbL-films that would completely be removed by a few rubbing cycles in the absence of a protective coating. A 45 nm thick LbL-film composed of gold nanoparticles and poly(allylamine hydrochloride) was chosen as an especially weak example for a functional multilayer system. The critical thickness for the protective LbL-coatings on top of the weak multilayer was determined to be about 6 layer pairs corresponding to about only 10 nm. At this thickness, the whole film withstands at least 25 abrasion cycles with a reduction of the total thickness of only about 2%. © 2013 American Chemical Society.

Mesbah A.,CNRS Jean Lamour Institute | Mesbah A.,CNRS Marcoule Institute for Separative Chemistry | Rabu P.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Rabu P.,International Center for Frontier Research in Chemistry | And 5 more authors.
Inorganic Chemistry | Year: 2014

Dehydration of the hybrid compound [Ni3(OH)2(tp) 2(H2O)4] (1) upon heating led to the sequential removal of coordinated water molecules to give [Ni3(OH) 2(tp)2(H2O)2] (2) at T1 = 433 K and thereafter anhydrous [Ni2(OH)2(tp)] (3) at T2 = 483 K. These two successive structural transformations were thoroughly characterized by powder X-ray diffraction assisted by density functional theory calculations. The crystal structures of the two new compounds 2 and 3 were determined. It was shown that at T1 (433 K) the infinite nickel oxide chains built of the repeating structural unit [Ni 3(μ3-OH)2]4+ in 1 collapse and lead to infinite porous layers, forming compound 2. The second transformation at T2 (483 K) gave the expected anhydrous compound 3, which is isostructural with Co2(OH)2(tp). These irreversible transitions directly affect the magnetic behavior of each phase. Hence, 1 was found to be antiferromagnetic at TN = 4.11 K, with metamagnetic behavior with a threshold field Hc of ca. 0.6 T. Compound 2 exhibits canted antiferromagnetism below TN = 3.19 K, and 3 is ferromagnetic below TC = 4.5 K. © 2014 American Chemical Society.

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