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Polymeric Layers (polymeric + layer)

Distribution by Scientific Domains

Polymers and Materials Science	66%

Selected Abstracts

Synthesis of Poly(4-vinylpyridine) Thin Films by Initiated Chemical Vapor Deposition (iCVD) for Selective Nanotrench-Based Sensing of Nitroaromatics

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
Wyatt E. Tenhaeff
Abstract A new nanoscale sensing concept for the detection of nitroaromatic explosives is described. The design consists of nitroaromatic-selective polymeric layers deposited inside microfabricated trenches. As the layers are exposed to nitroaromatic vapors, they swell and contact each other to close an electrical circuit. The nitroaromatic selective polymer, poly(4-vinylpyridine) (P4VP), is deposited in the trenches using initiated chemical vapor deposition (iCVD). P4VP is characterized for the first time as a selective layer for the absorption of nitroaromatic vapors. The Flory,Huggins equation is used to model the swelling response to nitroaromatic vapors. The Flory,Huggins interaction parameter for the P4VP,nitrobenzene system at 40,°C is 0.71 and 0.25 for P4VP,4-nitrotoluene at 60,°C. Sensing of nitrobenzene vapors is demonstrated in a prototype device, while techniques to improve the performance of the design in terms of response time and sensitivities are described. Modeling shows that concentration and mass limits of detection of 0.95,ppb and 3 fg, respectively, can be achieved. [source]

Functional Chromium Wheel-Based Hybrid Organic,Inorganic Materials for Dielectric Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Vito Di Noto
Abstract The first example of organic,inorganic hybrid materials based on the embedding of a chromium,nickel wheel cluster {[(n-C3H7)2NH2]- [Cr7NiF8(O2C4H5)16]} (Cr7Ni) into poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described. By an optimized copolymerization of the methacrylate-functionalized chromium,nickel wheel with methyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneous hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01,Hz to 10,MHz and over the temperature range of 5,115,°C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the , and , relaxation modes of the PMMA matrix. The position of these modes shifts toward higher frequencies as temperature increases. BDS is a powerful tool revealing the intimate miscibility of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric constant of 2.9 at 25,°C and 1,kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spectroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embedded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (EPR) spectroscopic measurements. [source]

Modification of poly(ethylene terephthalate) surface with attached dextran macromolecules

POLYMER INTERNATIONAL, Issue 9 2009
Yurij Stetsyshyn
Abstract BACKGROUND: Peroxidation of a poly(ethylene terephthalate) (PET) surface clears the path to the formation of biospecific polymeric layers on it. The goal of this work was the modification of a PET surface with oligoperoxides with further grafting of dextran macromolecules to this peroxidated surface. RESULTS: Novel oligoperoxides with a good affinity to PET were synthesized. They are capable of attaching to the PET surface, due to the decomposition of peroxide groups via the formation of free radicals. The alterations in surface energy and its components as a result of surface modification as well as changes in topography of the PET surface were determined. The degree of modification of the PET surface can reach 68% and depends on the following: the method of oligoperoxide and dextran deposition; the concentration of both oligoperoxide and dextran in the initial solution; and the temperature at which the modification is carried out. CONCLUSION: A new method of PET surface activation has been developed. The attachment of dextran macromolecules to modified PET surfaces is confirmed. Copyright © 2009 Society of Chemical Industry [source]

Coordination polymers and hydrogen-bonded assemblies of 2,2,-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid with ammonium, lanthanum and zinc cations

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
Hatem M. Titi
We report the synthesis of the 2,2,-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid (TALH4) ligand and the structures of its adducts with ammonium, namely diammonium 2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetate, 2NH4+·C14H12O102,, (I), lanthanum, namely poly[[aquabis[,4 -2,2,-(2-carboxylatomethyl-5-carboxymethyl-1,4-phenylenedioxy)diacetato]dilanthanum(III)] monohydrate], {[La2(C14H11O10)2(H2O)]·H2O}n, (II), and zinc cations, namely poly[[{,4 -2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}zinc(II)] trihydrate], {[Zn(C14H12O10)]·3H2O}n, (III), and poly[[diaqua(,2 -4,4,-bipyridyl){,4 -2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}dizinc(II)] dihydrate], {[Zn2(C14H10O10)(C10H8N2)(H2O)2]·2H2O}n, (IV), the formation of all four being associated with deprotonation of TALH4. Adduct (I) is a diammonium salt of TALH22,, with the ions located on centres of crystallographic inversion. Its crystal structure reveals a three-dimensional hydrogen-bonded assembly of the component species. Reaction of TALH4 with lanthanum trinitrate hexahydrate yielded a two-dimensional double-layer coordination polymer, (II), in which the LaIII cations are nine-coordinate. With zinc dinitrate hexahydrate, TALH4 forms 1:1 two-dimensional coordination polymers, in which every ZnII cation is linked to four neighbouring TALH22, anions and each unit of the organic ligand is coordinated to four different tetrahedral ZnII cation connectors. The crystal structure of this compound accommodates molecules of disordered water at the interface between adjacent polymeric layers to give (III), and it has been determined with low precision. Another polymer assembly, (IV), was obtained when zinc dinitrate hexahydrate was reacted with TALH4 in the presence of an additional 4,4,-bipyridyl ligand. In the crystal structure of (IV), the bipyridyl and TAL4, entities are located on two different inversion centres. The ternary coordination polymers form layered arrays with corrugated surfaces, with the ZnII cation connectors revealing a tetrahedral coordination environment. The two-dimensional polymers in (II),(IV) are interconnected with each other by hydrogen bonds involving the metal-coordinated and noncoordinated molecules of water. TALH4 is doubly deprotonated, TALH22,, in (I) and (III), triply deprotonated, viz. TALH3,, in (II), and quadruply deprotonated, viz. TAL4,, in (IV). This report provides the first structural characterization of TALH4 (in deprotonated form) and its various supramolecular adducts. It also confirms the potential utility of this tetraacid ligand in the formulation of coordination polymers with metal cations. [source]

Square-grid coordination networks of diaquabis(4,4,-bipyridyl)copper(II) crosslinked by hydrogen bonds through two monoanions of 1-benzofuran-2,3-dicarboxylic acid and five molecules of water

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Rajesh Koner
The title compound, poly[[[diaquacopper(II)]-di-,-4,4,-bipyridyl] bis(3-carboxy-1-benzofuran-2-carboxylate) pentahydrate], {[Cu(C10H8N2)2(H2O)2](C10H5O5)2·5H2O}n, crystallizes in a single-framework architecture. It is composed of two-dimensional square-grid coordination networks of 1:2:2 copper,4,4,-bipyridine,water units, wherein each copper ion coordinates equatorially to four bipyridyl units and axially to two water ligands. The polymeric nets are intercalated by layers of the benzofurandicarboxylic acid monoanions and additional water species. An extensive array of hydrogen bonds interlinks the various components of the structure. The Cu atom and the bipyridyl entities are located on axes of twofold rotation. This study confirms the preferred monoanionic nature of the benzofurandicarboxylic acid molecule. It reveals a rarely observed extended coordination polymer composed only of copper ions and bipyridyl linkers, and an interesting hydrogen-bonding connectivity between the polymeric layers aided by the benzofurandicarboxylic acid and water components intercalated in the structure. [source]

SiOx-Based Multilayer Barrier Coatings Produced by a Single PECVD Process

PLASMA PROCESSES AND POLYMERS, Issue S1 2009
Alessandro Patelli
Abstract Multilayer organic/inorganic gas barrier coatings on plastics are needed for high performance demanding applications from OLEDs to packaging. In order to simplify the multilayer deposition process, we developed a single step vacuum process where silicon oxide-based PECVD multilayers are obtained by the modulation of the hexamethyldisiloxane (HMDSO) precursor inlet and interfaces are controlled by pumping speed. In this way, depending on O2/HMDSO ratio, ,ceramic' or ,polymeric' layers are deposited, with nanometre control of thickness of layers and interfaces. Permeability behaviour of the multilayer structures obtained is described as a function of the number of layers and their thickness. [source]