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| 16(22) (2000), 8501-8509
A new approach to creating patterned composite structures with layer-by-layer assembled thin films is introduced. In this approach, the top surfaces of layer-by-layer films are chemically patterned by the direct stamping of functional polymers on the surface. The resulting pattern is then used as a template for the further deposition of materials on the surface. This paper illustrates this concept through the patterning of an oligoethylene glycol resist atop a polyelectrolyte multilayer surface. The resist layer is created by stamping an oligoethylene oxide-maleic anhydride graft copolymer onto the top polyamine surface. Further deposition of polyions results in the formation of a patterned polymer film atop the original multilayer thin film. When a patterned polyelectrolyte film is used as the base layer or substrate in this process, a second pattern can be stamped atop the original patterned array. Subsequent selective adsorption of polymers yields a second level of microstructures, illustrating the concept of multiple level patterning for layer-by-layer thin films; this concept can be broadened to include selective deposition of numerous materials on top of multilayer polymer systems. [124] Design and Demonstration of Hybrid Multilayer Structures - Layer-by-Layer Mixed Covalent and Ionic Interlayer Linking Chemistry P. Kohli and G. J. Blanchard Langmuir 16(22) (2000), 8518-8524 We report on the growth of layered molecular assemblies where the interlayer attachment chemistry is controlled layer-by- layer. We demonstrate the compatibility of chemistry where the layers are connected by ionic coordination chemistry [ROPO32-- Zr4+--O2CR]+OH- and by the formation of covalent urea moieties. A maleimide-vinyl ether (MVE) copolymer containing pendant benzoic acid and butyl alcohol functionalities is used for ionic layer growth. Coupling of covalently bonded adlayers to the MVE polymer is achieved by the attachment of poly(ethylene imine), PEI, to the MVE surface. Subsequent reaction of the PEI surface with diisocyanates and diamines produces urea-linked covalent multilayers. The covalent multilayers can be converted to ionic growth chemistry by treatment of the aminated terminal surface with POCl3 and water followed by further reaction with MVE polymer and Zr4+ ions. We report the reaction schemes for these hybrid layer structures and the characterization of these novel materials by optical ellipsometry, FTIR and UV-vis spectroscopy, XPS, and X-ray diffraction. The data show the formation of robust multilayer assemblies characterized by limited order within each layer. [125] Films of Manganese Oxide Nanoparticles with Polycations or Myoglobin from Alternate-Layer Adsorption Y. Lvov, B. Munge, O. Giraldo, I. Ichinose, S. L. Suib and J. F. Rusling Langmuir 16(23) (2000), 8850-8857 Alternate adsorption of manganese oxide nanoparticles with polycations poly(dimethyldiallyl-ammonium) (PDDA) or myoglobin (Mb) onto silver, quartz, and rough pyrolytic graphite gave stable, porous, ultrathin films. Quartz crystal microbalance (QCM) and UV- vis absorbance revealed regular film growth at each adsorption step for MnO2 and PDDA and for SiO2 nanoparticles and Mb. Scanning electron microscopy of MnO2/PDDA films showed smooth surfaces on the 20 nm scale and cross sections consistent with individual nanoparticles. QCM during growth of films of Mb and MnO2 reflected a competition for adsorption of the protein by the film surface and dispersed MnO2 nanoparticles. Nevertheless, films of Mb and MnO2 up to 30 nm thick on rough pyrolytic graphite electrodes could be constructed These novel films featured reversible interconversion of the protein's heme Fe-III/Fe-II redox couple with 10 electroactive layers of protein, considerably more than for polyion-Mb films on smooth gold (ca. 1.3 electroactive layers), and coiled PSS/Mb, films on rough graphite (7 electroactive layers). Shifts in redox potential caused by CO complexation of the heme Fen, BET specific areas, and electrochemically driven catalytic reduction of oxygen suggest that the Mb/MnO2 films are highly porous to gas molecules. To our knowledge, these films represent the first nanofabrication of inorganic particles with functional proteins by the layer-by- layer method. [126] Steady-State and Time-Resolved Spectroscopy of a Self-Assembled Cyanine Dye Multilayer E. Rousseau, M. Vanderauweraer and F. C. Deschryver Langmuir 16(23) (2000), 8865-8870 Ultrathin organic multilayers, consisting of polyelectrolytes and J-aggregates of a cyanine dye, were obtained using the layer by layer alternate adsorption technique. Buildup of the multilayer is followed by UV-vis absorption spectroscopy. The fluorescence properties of the J-aggregates are studied by steady-state fluorescence spectroscopy and picosecond fluorescence decay measurements. Fluorescence of the cyanine dye, when adsorbed on the substrate, results in a narrow emission band with a small Stokes shift which is characteristic for J-aggregate emission. Time-resolved fluorescence measurements yield a very short average decay time, which can be attributed to the J-aggregates. These results describing the fluorescence properties of multilayer assemblies containing J- aggregates allow on to compare them to those of J-aggregates of the cyanine dye in solution. [127] Polyelectrolytes I - Polyanion/Polycation Multilayers at the Air/Monolayer/Water Interface as Elements for Quantitative Polymer Adsorption Studies and Preparation of Hetero- Superlattices on Solid-Surfaces J. Ruths, F. Essler, G. Decher and H. Riegler Langmuir 16(23) (2000), 8871-8878 Polyanion/polycation multilayers floating at the air/water interface were prepared by consecutive adsorption of polyelectrolyte layers onto a Langmuir monolayer from aqueous polyelectrolyte subphase solutions. With the positively charged Langmuir monolayer headgroups of the lipid dimethyldioctadecylammonium bromide, the layer sequence starts with the negatively charged polyelectrolyte polystyrene sulfonate. With the negatively charged monolayer dimyristoylphosphatidic acid, it starts with the positively charged polyallylamine. Equally charged monolayer headgroups and polyelectrolytes do not bind to each other. Consecutive subphase exchange cycles of polyelectrolyte solutions with alternating charges and pure solvent in between lead to the formation of floating multilayers consisting of an alternating polyelectrolyte sequence. Ellipsometric measurements show that the thickness (adsorbed amount per unit area) of the multilayer film at the air/water interface grows in proportion to the number of adsorbed polyelectrolyte layers. The thickness of individual layers increases with increasing polyelectrolyte and/ or ion subphase concentration, respectively. The floating multilayers can be deposited as a sequence of layers of monomeric lipid and polyelectrolytes (hetero-superlattices) onto solid substrates via Langmuir-Blodgett transfer. UV- absorbance studies corroborate the quantitative interpretation of the ellipsometric data in terms of the polymer concentration in the layers, the individual layer thicknesses, and the adsorbed amounts per unit area. [128] Microencapsulation of Uncharged Low-Molecular-Weight Organic Materials by Polyelectrolyte Multilayer Self-Assembly F. Caruso, W. J. Yang, D. Trau and R. Renneberg Langmuir 16(23) (2000), 8932-8936 Two uncharged microcrystalline substances, pyrene (PYR) and fluorescein diacetate (FDA), were rendered water dispersible by treatment with various amphiphilic substances and subsequently encapsulated by exposure to an alternating sequence of cationic and anionic polyelectrolytes. The amphiphilic compounds employed to charge the microcrystals were ionic surfactants, phospholipids, and polyelectrolytes with an amphiphilic nature. Polyelectrolyte layers were self-assembled onto the pre-charged microcrystalline templates by means of electrostatic layer-by- layer deposition, thus forming a multilayered polymeric shell around the crystalline cores. The semipermeable nature of the polymer multilayer shell was thereafter exploited to remove the templated core by exposure to a mild organic solvent. The release behavior of solubilized PYR and FDA from the crystalline core was examined by monitoring their fluorescence after dissolution with ethanol. Complete removal of the core yielded hollow polymer capsules of micrometer dimensions. The capsule porosity was found to be influenced by the amphiphile used to pre-charge the microcrystal surface. The strategy presented is expected to be a general approach for the encapsulation of hydrophobic, low molecular weight compounds such as drugs, as well as providing a novel and facile pathway to the fabrication of polymer multilayered microcapsules with controlled release properties for drug delivery. [129] Adsorption-Induced 2nd-Harmonic Generation from the Layer-by- Layer Deposited Ultrathin-Film Based on the Charge-Transfer Interaction Y. Shimazaki, S. Ito and N. Tsutsumi Langmuir 16(24) (2000), 9478-9482 This paper is concerned with the second harmonic generation (SHG) from as deposited layer-by-layer adsorbed films. A nanolayered film was fabricated through the intermolecular charge-transfer interaction between the electron-donating carbazole (Cz) group and electron-accepting 3,5-dinitrobenzoyl group in the side chains of methacrylate-based polymers. A nonlinear optical dye was introduced in the film by using the copolymer in which Cz and disperse red 1 (DR1) groups were attached to the side chains. The DR1 moiety was highly oriented through the adsorption of PCzEMA-DR1, and the orientation was relaxed by additional adsorption of the polymers onto the DR1- containing layer, The second harmonic (SH! intensity of the multilayered film remained almost constant for the layers of even and odd numbers. This behavior could be explained by considering the change in the nonlinear susceptibility of the succeeding DR1-containing layer. The SH intensity kept constant up to 120 degreesC for thermal stability. [130] Enzyme Multilayers on Colloid Particles - Assembly, Stability, and Enzymatic-Activity F. Caruso and C. Schuler Langmuir 16(24) (2000), 9595-9603 Colloidal biocatalysts, comprising polystyrene (PS) carrier particles coated with enzyme multilayers, were fabricated via the layer-by-layer self-assembly method. Glucose oxidase (GOD), horseradish peroxidase (POD), or preformed enzyme- polyelectrolyte complexes were assembled in alternation with oppositely charged polyelectrolytes onto PS particles. Microelectrophoresis, single-particle light scattering, and transmission electron microscopy confirmed stepwise growth of the multilayer films on the colloid particles. The high surface area Enzyme multilayer-coated particles were successfully employed as specific enzyme reactors (i.e., as catalysts). Whereas no loss in activity was observed for the enzymes immobilized directly onto particle surfaces, precomplexing the enzymes with polymer in solution drastically reduced their activity (by up to 70%). The enzymatic activity (per particle) was found to increase with the number of enzyme layers immobilized, irrespective of whether the enzyme was precomplexed. However, particles coated with preformed enzyme- polyelectrolyte complexes displayed a significantly lower enzymatic activity than those fabricated by the direct adsorption of free enzyme. Multicomponent films of GOD and POD on colloid particles were also prepared, and sequential enzymatic catalysis was demonstrated. Furthermore, experiments were conducted with particles exhibiting both magnetic and catalytic functions. These particles, premodified with a layer of magnetic nanoparticles to impart a magnetic property and subsequently coated with enzyme multilayers, were repeatedly used as catalysts following their rapid and easy separation with a magnet. Such biocolloids are expected to find applications in biotechnology. [131] Layer-by-Layer Self-Assembly of Organic-Organometallic Polymer Electrostatic Superlattices Using Poly(Ferrocenylsilanes) M. Ginzburg, J. Galloro, F. Jakle, K. N. Powerbillard, S. M. Yang, I. Sokolov, C. N. C. Lam, A. W. Neumann, I. Manners and G. A. Ozin Langmuir 16(24) (2000), 9609-9614 Water-soluble poly(ferrocenylsilane) (PFS) and poly(styrenesulfonate) (PSS) of alternating charge are shown to self-assemble in a layer-by-layer fashion on primed Au, Si, and quartz substrates to create the first examples of organic- organometallic electrostatic superlattices from polymers with ferrocene units in the backbone. The layer-by-layer assembly of these electrostatic superlattices has been monitored through frequency changes with layer deposition using a quartz-crystal microbalance (QCM), a regular film thickness increase observed using ellipsometry, and step-wise absorbance increases observed using ultraviolet-visible (UV-vis) spectroscopy. As well, structural information was obtained using X-ray photoelectron spectroscopy (XPS), water contact angle measurements, and atomic force microscopy (AFM). These superlattices are of interest as possible precursors to patterned magnetic and redox active multilayers. [132] Amphoterization of Colloidal Gold Particles by Capping with Valine Molecules and Their Phase-Transfer from Water to Toluene by Electrostatic Coordination with Fatty Amine Molecules A. Kumar, P. Mukherjee, A. Guha, S. D. Adyantaya, A. B. Mandale, R. Kumar and M. Sastry Langmuir 16(25) (2000), 9775-9783 The surface modification of colloidal gold particles with the amino acid valine is demonstrated. Self-assembly of valine on the gold particles is accomplished in the aqueous phase, linkage with the gold particles possibly occurring through covalent interaction of the amine group with the surface gold atoms. Derivatization with the amino acid in this manner imparts amphotericity to the gold particles, the particles being negatively charged at pH values greater than 6 (the isoelectric point of valine) and positively charged below this pH. The charge reversal on the gold particles is demonstrated by electrostatic self-assembly of the colloidal gold particles on glass (which is negatively charged at pH > 3) by immersion of the substrate alternately into the valine-capped gold solutions maintained at pH = 3.5 and 8.5. The phase transfer of the aqueous valine-capped gold colloidal particles by electrostatic linkage with fatty amine molecules present in toluene is also described. The two-phase method described herein is extremely simple and results in hydrophobic gold particles which may be precipitated out of solution and redissolved in different nonpolar organic solvents without significant variation in the particle size distribution. The electrostatically driven multilayer assembly of the valine- derivatized gold particles on glass substrates, the phase transfer process, and the stability of the hydrophobized gold particles have been investigated with a variety of techniques such as UV-vis, infrared and X-ray photoemission spectroscopies, ellipsometry, and thermogravimetry/differential thermal analyses. [133] Modeling of the Salt Permeability in Fixed Charge Multilayer Membranes K. Lebedev, P. Ramirez, S. Mafe and J. Pellicer Langmuir 16(25) (2000), 9941-9943 [134] Sprayed Polyelectrolyte Multilayers J. B. Schlenoff, S. T. Dubas and T. Farhat Langmuir 16(26) (2000), 9968-9969
[135] The Role of Secondary Interactions in Selective Electrostatic Multilayer Deposition S. L. Clark and P. T. Hammond Langmuir 16(26) (2000), 10206-10214 Electrostatic layer-by-layer thin films maybe directed to specific regions of a surface based on electrostatics, secondary interactions, and steric repulsion. In this study, a series of polyamines ranging from hydrophobic polyallylammonium hydrochloride (PAH) to hydrophilic linear polyethyleneimine (LPEI) were coadsorbed with poly(acrylic acid) (PAA) onto patterned self-assembled monolayer (SAM) surfaces. When an acid (COOH) and oligoethylene glycol (EG) SAMs are used as the surface template, it was found that the region of preferred deposition for the more hydrophobic polyamine species was generally the EG region at pH 4.8, rather than the partially charged COOH region. The more hydrophilic LPEI species preferred adsorption on the COOH surface. It is proposed that PAH undergoes complexation with the EG surface based on hydrophobic and hydrogen bonding interactions at moderate pH. On the other hand, the LPEI backbone is hydrated and is thought to undergo large steric repulsion with the EG surface, thus resulting in deposition only on the COOH surface. The region of preferred adsorption also varied with pH, as the hydrogen- bonding interaction of PAA became important at low pH, and electrostatic interactions became the controlling element for selectivity at high pH, when all systems were highly charged. By tuning polyion-surface interactions, the region of polyion deposition can be carefully controlled on patterned chemical surfaces. [136] Ultrathin-Film Self-Assembly of Hybrid Organic-Inorganic Metal Coordination Polymers H. Byrd, C. E. Holloway, J. Pogue, S. Kircus, R. C. Advincula and W. Knoll Langmuir 16(26) (2000), 10322-10328 We have investigated the self-assembly of ultrathin zirconium coordination monomer and polymer films using a layer-by-layer approach. These materials are of great interest for incorporating metal ion (inorganic) moieties in organic (polymer) films with applications ranging from conductors to catalytic materials. The differences between the polymer and monomer assembly from solution are described. These differences were investigated using UV-vis spectroscopy, AFM, and surface plasmon spectroscopy. The differences in orientation, morphology, roughness, and linearity of deposition reflect the conformational limitations of the polymer toward self-assembly. On the other hand, the sequential assembly of the monomer and Zr metal ion indicates the strong coordination between the metal and the organic ligands, resulting in robust homogeneous films. [137] Thin-Film Optical Sensors Employing Polyelectrolyte Assembly S. H. Lee, J. Kumar and S. K. Tripathy Langmuir 16(26) (2000), 10482-10489 This work describes the development of thin film optical sensors for pH, metal ions (ferric and mercury), and 2,4- dinitrotoluene detection. To fabricate the pH sensor, a fluorescent molecule, 1-hydroxypyren-3,6,8-trisulfonate, was assembled with a polycation by an electrostatic layer-by-layer assembly technique. The fluorescent indicator molecule exhibits distinct and well-defined emission peaks for protonated and deprotonated forms. The relative peak positions and intensity of fluorescence of the protonated and deprotonated forms change in response to pH variations. For metal ion (ferric and mercury) and 2,4-dinitrotoluene sensing, the indicator molecules were covalently incorporated into poly(acrylic acid) and subsequently assembled with a polycation employing electrostatic layer-by-layer assembly. The sensor is based on the fluorescence quenching of indicator molecules by electron transfer from indicator to electron-deficient analytes such as ferric ions, mercury, and 2,4-dinitrotoluene. Fluorescence intensities decreased with increasing concentration of analytes, Quenching behavior follows Stern-Volmer bimolecular quenching kinetics. Linear increase in absorbance, film thickness, and emission intensity was observed as a function of number of bilayers deposited in all these films. [138] Multilayer Assemblies of Copolymer Psoh and PVP on the Basis of Hydrogen-Bonding L. Y. Wang, S. X. Cui, Z. Q. Wang, X. Zhang, M. Jiang, L. F. Chi and H. Fuchs Langmuir 16(26) (2000), 10490-10494 An alternating deposition film of a copolymer of p-(hexaflouro- 2-hydroxylisopropyl)-alpha -methylstyrene and styrene (PSOH) and poly(4-vinylpyridine) (PVP) was fabricated on the basis of hydrogen bonding between hydroxyl and a pyridine ring in chloroform. It is found that the selection of solvent is very important for successful preparation of a multilayer film on the basis of hydrogen bonding. A series of PSOHs with different contents of hydrogen-bonding donors were used to fabricate multilayer assemblies. The driving force for multilayer assemblies was identified by FTIR. Several factors, such as solvents, concentration, and content of hydrogen-bonding donors, were discussed, which influence greatly the deposition process and layered architectures. [139] Preparation of Microcapsules of Strong Polyelectrolyte Couples by One-Step Complex Surface Precipitation A. Voigt, E. Donath and H. Möhwald MACROMOL MATER ENG 282(9) (2000), 13-16 Full Paper: Polyelectrolyte microcapsules are fabricated by a one-step surface precipitation and by a layer-by-layer technique an decomposable colloids. The ternary solvent water/ acetone/sodium bromide is adjusted properly keeping dissolved simultaneously the strong polyelectrolytes sodium poly(styrene sulfonate) and poly(vinyl benzyl trimethylammonium chloride). Microcapsules are characterized by confocal laser scanning microscopy and scanning force microscopy. The capsules are dissolvable in the ternary solvent. Other dissolved strong polyelectrolyte couples and template-free preparation pathways are suggested. [140] Self-Assembly of Mono-Layer and Multilayer of Polyconjugated Conducting Polymers A. Berlin and G. Zotti MACROMOL RAPID COMMUN 21(7) (2000), 301-318 To obtain organised mono- and multilayers of policonjugated polymers or oligomers by self assembly techniques has recently attracted much attention. This is due to the simplicity of the method and to the fact that no sophisticated apparatus is required. In the present feature the state of the art in this field is discussed including our own research results. A survey on self assembly of thiols, disulfides, and alkylsilanes on gold or glass surfaces is presented as well as self assembly of ferrocenylalkyl-substituted heterocycle adsorbates on ITO surfaces. Carboxyalkyl bithiophenes and terthiophenes, in which the oligothiophene tail is either perpendicularly or linearly linked to the tethering carboxyalkyl chain form stable monolayers on ITO electrodes and are anodically oxidised to produce polymer layers or to couple with oligothiophenes in solution, depending on the structure. As for multilayers, an introductory survey on the self assembly technique usually employed is given. Several examples of multilayers constituted of electroconductive polymers are discussed. Finally our recent results concerning different multilayers from polythiophenes bearing anionic and cationic moieties are discussed. [141] Ultrathin Polymer-Coatings by Complexation of Polyelectrolytes at Interfaces - Suitable Materials, Structure and Properties P. Bertrand, A. Jonas, A. Laschewsky and R. Legras MACROMOL RAPID COMMUN 21(7) (2000), 319-348 The article presents the state-of-the-art of alternating physisorption of oppositely charged polyelectrolytes, the so- called ''layer-by-layer'' method or ''electrostatic self- assembly'' (ESA), for the preparation of thin polymer coatings. In comparison to other, more established self-organization techniques, this recent method is distinguished by its simplicity, versatility, and speed. In particular, the tendency for self-healing is unique. Emphasis is given to the role of the molecular structure of the polyelectrolytes, and to the nature of the support. Also, various parameters for the preparation of multilayer films are highlighted, which are very important due to the kinetic control of the build-up process. The structure of the resulting coatings, their quality and stability, chemical reactions in the films, and potential applications are discussed. [142] Preparation of Enzyme Multilayers on Colloids for Biocatalysis C. Schuler and F. Caruso MACROMOL RAPID COMMUN Yüklə 0,52 Mb. Dostları ilə paylaş:
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